Multi-Layer Thermoplastic Spray Coating System for High Performance Sealing on Airplanes

ABSTRACT

Tunable multi-layer thermoplastic polymer sealants and tunable two-layer conductive thermoplastic polymer sealants, and substrates and assemblies comprising the tunable multi-layer sealants; and edge seals and fillet seals produced comprising such sealants; and substrates, components and objects comprising the tunable edge seals and fillet seals, and methods for making and applying such edge seals and fillet seals are disclosed.

TECHNOLOGICAL FIELD

The present disclosure relates generally to the field of coatings andsealants. More specifically the present disclosure relates to the fieldof coatings and sealants, including conductive coatings and sealants,particularly those coatings and sealants applied to a surface by thermalspraying.

BACKGROUND

In many fields, components on large structures, including those found onvehicles, including aircraft, etc., are typically coated with paints,primers, coatings, etc. that can provide a number of functions to asubstrate surface, including, for example, protection from corrosion andother forms of environmental degradation, overcoat or sealant adhesion,abrasion resistance, appearance, etc. Coatings and sealants are oftenapplied to areas of assembled components or sub-assemblies that aredifficult to access through traditional coating and sealant applicationprocesses. In addition, a significant number, sometimes numbering in thethousands and tens of thousands, of small parts (e.g., fasteners, etc.)and areas requiring sealing (e.g., edge seals and fillet seals, etc.)requiring coatings and/or sealants can occur in assemblies in a largestructure (e.g., fuel tanks on aircraft, etc.). Further, many coatingsand sealants require lengthy curing protocols, or require applying heator other added triggering mechanism (e.g. ultraviolet radiation, etc.)to obtain an appropriate degree of curing.

Further, some coatings (e.g. paints and primers, etc.) and sealants areoften electrically insulative and can result in an impediment to thedissipation of static and other electrical charges. Certain structuresrequire the need to dissipate electrical charges that build up on astructure's interior and/or exterior surfaces, including staticelectrical charges, and charges resulting from, for example lightningstrikes, etc. The need to consider electrical charge dissipationcontinues in the aircraft industry, as aircraft manufacture continues toincorporate non-metallic materials. Further, in certain aircraftassemblies, non-metallic materials, such as composites, plastics, etc.,that do not dissipate electrical charges predictably across theirsurfaces may be joined with, or otherwise contact, assemblies andsub-assemblies that comprise metallic materials that do conductelectrical charges. That is, components, assemblies and sub-assembliesthat include both composite and metallic materials may be used in themanufacture of, or otherwise incorporated into, larger structures (e.g.aircraft).

Such structures may encounter electromagnetic effects (EMEs) including,for example, and without limitation, lightning strikes. When a structureencounters an EME, the charge delivered to the structure travelsthroughout any conductive path, and can cause damage to exposeddielectric materials including, for example, composite materials. Theelectrical damage to composite materials from EMEs can be exacerbated ifthe edges of the composite material comprise exposed carbon fibers. Ifthe path of charges resulting from an EME encounters varying materialshaving varying conductivities, damage at or near the material interfacecan occur. Such interfaces include, without limitation,fasteners/substrate interfaces, and can further include joinedinterfaces where, for example, seals (e.g., fillet seals, edge seals,etc.) occur.

Carbon fiber reinforced plastic materials (CFRPs) have utility instructures including, without limitation, vehicles including, withoutlimitation, aircraft. CFRPs comprise a fiber material (e.g. carbonfibers, etc.) impregnated with a resin material (e.g. epoxy resin,acrylic resin, etc.) to make so-called prepregs. Prepregs are partiallycured layers that can be manufactured into rolls that can yield unrolledsheets for use in composite material manufacture. Prepreg material, or“prepregs” can then be “laid-up” or “stacked” into multi-layered“stacks” that can be shaped on forming mandrels or other tooling,followed by curing or partially curing the shaped material to produce acomposite material that, if desired, adopts desired and predeterminedshapes and dimensions imparted by the tool, with the composite materialhaving desired weight and strength. Alternately, prepregs may beoriented into a stack that is trimmed and cured to form a solid stackfor use as a composite material structure or other type of compositecomponent.

In aircraft manufacture, CFRP parts are often joined to other CFRP partsas well as other metallic parts and non-metallic parts. Problems canoccur with respect to predictably dissipating electrical charges whenmaterials, such as CFRPs and various metals (e.g. aluminum, titanium,etc.) that have differing conductivities are joined, fastened, or areotherwise in close proximity to one another. Such interfaces can sustainEME damage in the course of EME events such as, for example, staticdischarge and/or lightning strikes where electrical current builds upand is not dispersed efficiently due to the presence of materials havingdiffering conductivities/resistivities, as electrical charges move alonga pathway. This is especially problematic at component interfaces wheretwo materials are joined or in contact with one another and thematerials have varying resistivity values (e.g., where a firstsubstrate/component/part is made from a conductive material and isjoined to or positioned proximate to a second substrate/component/partmade from a non-conductive material or a material with a significantlydifferent conductivity/resistivity as compared to the firstsubstrate/component/part.

Coatings, especially coatings used in aircraft manufacture, also must berobust enough to possess a plurality of characteristics and may notadequately provide all of the required functions to an equivalent oracceptable degree. For example, conductive coatings for dissipatingelectrical charges across metallic and non-metallic coatings alike havebeen tried with varying success. Typically, the known conductivecoatings must be loaded with conductive particles to such an extent(sometimes as much as from about 50 to about 70 weight percent), thatother required coating characteristics suffer. Further, such heavilyloaded conductive coatings can make certain coating applicationtechniques difficult or impossible (e.g., high viscosity coatingmaterials typically cannot be applied using, for example, spraytechniques, etc.).

In addition, surface coatings that may be designed to alleviateelectrical imbalances across various metallic and/or non-metallicsurfaces must often, at least in part, address additional concerns andfunctions including appearance, adhesion, abrasion resistance,environmental degradation, etc.

Further, inherent coating characteristics (viscosity, etc.,) may make itdifficult to apply such coatings to restrictive locations and surfacesusing efficient application techniques. For example, an otherwisedesirable coating may be too viscous to apply to a surface usingsprayers, when an application mode such as spraying could otherwiseoffer improvements to coating processing in terms of, efficiency, costsavings, etc.

In addition, specialized coatings having a useful range of varyingproperties may be expensive to prepare, maintain, store, or deploy.Otherwise useful coatings may further have long curing times, forexample taking days to cure with or without the presence of elevatedcuring temperatures or the use of additional triggering processes. Suchextended or complex curing regimens further add to the manufacturingtime required, as well as increasing cost. In addition, specializedcoatings may lack an adequate shelf life or pot life to be useful forvery long on-site. It may further be economically impractical for aparticular manufacturing facility (in terms of equipment or spacerequirements) to store and/or inventory coatings that require, forexample, maintenance at particular temperatures.

SUMMARY

According to the present disclosure, one aspect discloses a seal, theseal including at least a first thermoplastic polymer layer applied to asubstrate, with the first thermoplastic polymer layer adhering to thesubstrate at an adherence value ranging from about 10 lbs/in to about 30lbs/in wide area from a 90° peel test according to ASTM D6862-11 (2016)Standard Test Method for 90° Peel Resistance. The sealant furthercomprises a second thermoplastic polymer layer deposited onto the firstthermoplastic polymer layer, with the second thermoplastic polymer layerhaving a chemical resistance value to volatiles. According to furtheraspects, the second thermoplastic polymer layer has predeterminedcharacteristics, including a chemical resistivity characteristic of lessthan about 10% weight gain and less than 10% mechanical propertyreduction.

According to another aspect, the first thermoplastic polymer layerincludes at least one of: a thermoplastic co-polyester, a co-polymer ofvinylidene fluoride and hexafluoropropylene, a thermoplasticpolyurethane, a thermoplastic vulcanizate, a thermoplastic polyolefinelastomer, a styrene block co-polymer, a fluoroelastomer, andcombinations thereof.

According to a further aspect, the second thermoplastic polymer layerdeposited onto said first thermoplastic polymer layer comprises at leastone of: a polyether ether ketone, a polyether ketone ketone, apolyamide, a polysulfone, a polyphenylsulphone, a polyetheramide, andcombinations thereof.

In another aspect, the first thermoplastic polymer layer applied to thesubstrate comprises a modulus value of less than 1000 MPa having anelongation at break greater than 100%.

In a further aspect, the second thermoplastic polymer layer has modulusvalue of less than about 4 MPa with an elongation at beak of greaterthan about 20%.

In another aspect the second thermoplastic polymer layer has a chemicalresistance to long term jet fuel exposure measured in terms of incurringless than 10% weight gain.

A further aspect discloses an assembly comprising a first substrate anda second substrate, with the first and second substrates locatedproximate to one another, and a sealant located on at least one of thefirst and second substrates. The sealant includes at least a firstthermoplastic poly ranging from about 10 lbs/in to about 30 lbs/in widearea from a 90° peel test according to ASTM D6862-11 (2016) StandardTest Method for 90° Peel Resistance.

In a further aspect, the sealant further comprises a secondthermoplastic polymer layer deposited onto the first thermoplasticpolymer layer, with the second thermoplastic polymer layer having achemical resistance characteristic and chemical resistance value toenvironmental volatiles (e.g., jet fuel, etc.), with one chemicalresistance value being less than about a 10% weight gain when exposed toan environmental volatile material such as, for example, jet fuel.

Another aspect discloses an assembly including a first substrate and asecond substrate, with the first substrate including a first substrateedge and the second substrate including a second substrate edge. Thesecond substrate is located or otherwise oriented proximate to the firstsubstrate to form a substrate interface at a juncture between the firstsubstrate and the second substrate. A spray-deposited polymer sealant isconfigured to form a multi-layered thermoplastic polymer seal at thesubstrate interface.

According to a further aspect, a method is disclosed includingdelivering a spray-deposited multiple-layered thermoplastic polymersealant to a substrate surface, with the multi-layered thermoplasticpolymer sealant comprising at least two layers. The multi-layeredthermoplastic polymer sealant is delivered to the substrate surface inat least two layers to form the multiple-layered thermoplastic polymerseal; including a first thermoplastic polymer layer deposited onto thesubstrate surface, and a second thermoplastic polymer layer depositedonto the first thermoplastic polymer layer, with the first and secondthermoplastic polymer layers comprising a thermoplastic polymer thatdiffers from one another.

According to further aspects, the multi-layered thermoplastic polymerseal includes at least one of: a fillet seal located at the substrateinterface between the first and second substrates; an edge seal locatedat one or more of the first substrate edges and/or at one or more of thesecond substrate edges, and a fastener seal at the interface of afastener and a substrate surface.

According to a further aspect, the first thermoplastic polymer layer(deposited onto the substrate surface) includes at least one of: athermoplastic co-polyester, a co-polymer of vinylidene fluoride andhexafluoropropylene, a thermoplastic polyurethane, a thermoplasticvulcanizate, a thermoplastic polyolefin elastomer, a styrene blockco-polymer, a fluoroelastomer, and combinations thereof.

In a further aspect, the spray-deposited first thermoplastic polymerlayer (deposited onto a substrate surface) includes at least onethermoplastic polymer including at least one of: copolymers includingHytrel® TPC-ET (DuPont®), thermoplastic elastomers, and thermoplasticfluoroelastomers including DAI-EL® T-530 (Daikin®), and combinationsthereof.

In another aspect, the spray deposited second thermoplastic polymerlayer (deposited onto the first thermoplastic polymer layer) is madefrom a material including at least one of: thermoplastic polymersincluding, without limitation, a nylon, a polyetheretherketone, apolyetherketoneketone, a polyamide, a polyphenylsulfide, apolyphenylsulfone, a polysulfone, a polyetheramide, and combinationsthereof.

In another aspect, at least one of the first and second thermoplasticpolymer sealant materials further includes a conductive material, withthe conductive material including at least one of: titanium, nickelalloy, copper, carbon black, graphene powder, carbon nanotubes, andcombinations thereof.

Further aspects disclose methods including directing a firstthermoplastic polymer from a first thermoplastic polymer feedstock to afirst high-velocity sprayer, depositing the first thermoplastic polymerfrom the high-velocity sprayer onto a substrate surface, and forming afirst thermoplastic polymer layer on the substrate surface, with thefirst thermoplastic polymer layer having an adhesion value ranging fromabout 10 lbs/in to about 30 lbs/in wide area from a 90° peel test. Themethod further includes directing a second thermoplastic polymer from asecond thermoplastic polymer feedstock to a first or secondhigh-velocity sprayer, depositing the second thermoplastic polymer fromthe first or second high-velocity sprayer onto the first thermoplasticpolymer layer, forming a second thermoplastic polymer layer on the firstthermoplastic polymer layer, and forming a two-layer thermoplasticpolymer seal, with the second thermoplastic polymer layer having achemical resistance characteristic of less than about 10% weight gainand less than 10% mechanical property reduction.

In a further aspect, the spray-deposited first thermoplastic polymerlayer (deposited onto a substrate surface) includes at least onethermoplastic polymer comprising at least one of: a thermoplasticco-polyester, a copolymer of vinylidene fluoride andhexafluoropropylene, a thermoplastic polyurethane, a thermoplasticvulcanizate, a thermoplastic polyolefin elastomer, a styrene blockco-polymer, a fluoroelastomer, and combinations thereof.

In another aspect, the spray-deposited first thermoplastic polymer layer(deposited onto a substrate surface) includes at least one thermoplasticpolymer comprising at least one of: copolymers including Hytrel® TPC-ET(DuPont®), thermoplastic elastomers, and thermoplastic fluoroelastomersincluding DAI-EL® T-530 (Daikin®), and combinations thereof

In another aspect, the spray deposited second thermoplastic polymerlayer (deposited onto the first thermoplastic polymer layer) is madefrom a material that includes one or more thermoplastic polymersincluding, without limitation, a nylon, a polyetheretherketone, apolyetherketoneketone, a polyamide, a polyphenylsulfide, apolyphenylsulfone, a polysulfone, polyetheramide, and combinationsthereof.

The features, functions and advantages that have been discussed can beachieved independently in various aspects or may be combined in otheraspects, further details of which can be seen with reference to thefollowing description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described variations of the disclosure in general terms,reference will now be made to the accompanying drawings, which are notnecessarily drawn to scale, and wherein:

FIG. 1 is an illustration of an aspect of the present disclosure showinga thermoplastic polymer feedstock and a system including thethermoplastic polymer feedstock and a high-velocity sprayer fordepositing a thermoplastic polymer coating onto a substrate surface oronto a first thermoplastic polymer coating layer;

FIG. 2A is an illustration of an aspect of the present disclosureshowing the mixing of more than one thermoplastic polymer feedstocks toform a thermoplastic polymer feedstock mixture for use as a sprayformulation, and a system including the thermoplastic polymer feedstockmixture and a high-velocity sprayer for depositing a tunablethermoplastic polymer coating onto a substrate surface or onto a firstthermoplastic polymer coating layer;

FIG. 2B is an illustration of an aspect of the present disclosureshowing a plurality of thermoplastic polymer feedstocks delivered viaseparate feedlines to the sprayer shown in FIG. 2A, and a system fordepositing a tunable thermoplastic polymer coating onto a substratesurface or onto a first thermoplastic polymer coating layer;

FIG. 3A is an illustration of an aspect of the present disclosureshowing at least one thermoplastic polymer feedstock mixed with at leastone conductive feedstock to form a conductive thermoplastic feedstockmixture, and a system including the conductive thermoplastic polymerfeedstock mixture and a high-velocity sprayer for depositing aconductive thermoplastic polymer coating onto a substrate surface oronto a first thermoplastic polymer coating layer;

FIG. 3B is an illustration of an aspect of the present disclosureshowing at least one thermoplastic polymer feedstock and a conductivefeedstock shown in FIG. 3A, and a system including a high-velocitysprayer for depositing a conductive thermoplastic polymer coating onto asubstrate surface or onto a first thermoplastic polymer coating layer,with more than one thermoplastic polymer feedstock and the one or moreconductive feedstock delivered or directed to the sprayer via separatefeed lines;

FIG. 4A is an illustration of an aspect of the present disclosureshowing more than one thermoplastic polymer feedstocks mixed with aconductive feedstock to form a conductive thermoplastic polymerfeedstock mixture, and a system including the conductive thermoplasticpolymer feedstock mixture and a high-velocity sprayer for depositing aconductive thermoplastic polymer coating onto a substrate surface oronto a first thermoplastic polymer coating layer;

FIG. 4B is an illustration of an aspect of the present disclosureshowing two different thermoplastic polymer feedstocks and a conductivefeedstock shown in FIG. 4A, and a system including the two differentthermoplastic polymer feedstocks, the conductive feedstock and ahigh-velocity sprayer for depositing a conductive thermoplastic polymercoating onto a substrate surface or onto a first thermoplastic polymercoating layer, with the two thermoplastic polymer feedstocks and theconductive feedstock delivered or directed to the sprayer via separatefeed lines;

FIG. 5 is an illustration of an aircraft comprising assemblies andsubassemblies that further comprise fasteners having coatings accordingto aspects of the present disclosure, with the fasteners coated usingsystems and coated via methods according to aspects of the presentdisclosure;

FIG. 6A is a flowchart outing a method according to aspects of thepresent disclosure;

FIG. 6B is a flowchart outing a method according to aspects of thepresent disclosure;

FIG. 7A is a flowchart outing a method according to aspects of thepresent disclosure;

FIG. 7B is a flowchart outing a method according to aspects of thepresent disclosure;

FIG. 8A is a flowchart outing a method according to aspects of thepresent disclosure;

FIG. 8B is a flowchart outing a method according to aspects of thepresent disclosure;

FIG. 9 is an illustration of a thermal coating process according to apresent aspect;

FIG. 10 is an illustration of an aspect of the disclosure showing ahigh-velocity sprayer coating the underside of a fastener in place in anassembly;

FIG. 11 is an illustration showing fasteners according to aspects of thepresent disclosure in position in an assembly; and

FIG. 12 is a cross-sectional side view of a coated fastener in anassembly according to aspects of the present disclosure;

FIG. 13 is a top view of a coated fastener according to aspects of thepresent disclosure;

FIG. 13 is a flowchart outlining methods according to aspects of thepresent disclosure;

FIG. 14A is a flowchart outlining methods according to aspects of thepresent disclosure;

FIG. 14B is a flowchart outlining methods according to aspects of thepresent disclosure;

FIG. 15A is a flowchart outlining methods according to aspects of thepresent disclosure;

FIG. 15B is a flowchart outlining methods according to aspects of thepresent disclosure;

FIG. 16A is an illustration of two parts, or substrates fastenedtogether in an assembly and forming fillet seals at their juncture andhaving fillet seals and edge seals with sealant applied according toaspects of the present disclosure;

FIG. 16B is an enlarged cross-sectional view of the assembly shown inFIG. 16A;

FIG. 17 is an illustration of a fillet seal with a sealant appliedaccording to an aspect of the present disclosure;

FIG. 18 is an illustration of a fillet seal with a sealant appliedaccording to an aspect of the present disclosure;

FIG. 19 is an illustration of a fillet seal with a sealant appliedaccording to an aspect of the present disclosure;

FIG. 20A is a flowchart outlining methods according to aspects of thepresent disclosure;

FIG. 20B is a flowchart outlining methods according to aspects of thepresent disclosure;

FIG. 21A is a flowchart outlining methods according to aspects of thepresent disclosure;

FIG. 21B is a flowchart outlining methods according to aspects of thepresent disclosure;

FIG. 22 is a flowchart outlining methods according to aspects of thepresent disclosure; and

FIG. 23 is a flowchart outlining methods according to aspects of thepresent disclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure are directed to multi-layerthermoplastic polymer sealants, including sealants comprising a firstthermoplastic polymer layer, selected for having a first set ofparticular desired characteristics or properties, and that can beapplied to a substrate surface via a high-power sprayer that may be athermal sprayer. The presently disclosed sealants further comprise asecond thermoplastic polymer layer applied to the deposited firstthermoplastic polymer layer via a high-power sprayer that can be athermal sprayer. The second thermoplastic polymer is selected for havinga second set of particular desired characteristics or properties, withat least one characteristic or property being different from the firstdeposited thermoplastic polymer layer.

The first and/or second thermoplastic polymer feedstock can be athermoplastic feedstock formulation that can be tunable, or otherwisehave feedstock characteristics changed in real time during polymermaterial deposition. The feedstock materials can include or be providedwith varying amounts of conductive materials, making the resultingdeposited thermoplastic polymers conductively tunable by alteringamounts introduced to or from the respective feedstocks. Thethermoplastic polymer feedstock formulations can further be a powderedthermoplastic polymer feedstock formulation. The resulting first andsecond thermoplastic polymer layers are selected to be different fromeach other (and the respective thermoplastic polymer feedstock areselected to be different from one another), with the resulting first andsecond thermoplastic polymer layers each having predetermined anddesired characteristics and properties.

Aspects of disclosed two-layer thermoplastic coating formulations,including formulations that can contain a conductive material and thatcan be tuned or tailored, including in real time, provide a wide rangeof desired and predetermined characteristics in the formation of themulti-layer (and preferably two-layer) thermoplastic coatings. Thepresent coatings, that in combination form the at least a two-layerthermoplastic polymer sealant, provide robust protective qualities tothe substrates being coated with the presently disclosed two-layerthermoplastic polymer sealants.

When a conductive component is introduced into one or more of thethermoplastic polymer feedstocks that are directed to the high-velocitysprayer, electrically conductive thermoplastic polymer layers areproduced that can provide a particular, and wide-ranging amount ofpredetermined and desired resistivity or conductivity to the substratesbeing coated with the presently disclosed conductive thermoplasticcoatings.

Additionally, aspects of the present disclosure are directed tothermoplastic coating formulations that can be tailored to deliver athermoplastic coating using high-velocity spraying techniques tometallic and non-metallic substrates and components. When a conductivefeedstock material is present in the thermoplastic polymer feedstock,various characteristics of the resulting applied conductivethermoplastic polymer coatings can be predictably tailored, even insubstantially real-time, by changing the proportions of feedstockconstituents (e.g. the at least one thermoplastic polymer feedstock andthe conductive feedstock) that are provided to the high-velocitysprayer.

Without being limiting, when the feedstock is a powdered feedstock, theaverage particle size of the thermoplastic polymer powders usedaccording to aspects of the present disclosure range from about 20 μm toabout 300 μm. In addition, without being limiting, the average particlesize of the conductive powders used according to aspects of the presentdisclosure range from about 5 μm to about 80 μm.

The high-velocity sprayers used in connection with aspects of thepresent disclosure include sprayers able to disperse a feedstock atvelocities ranging from about 20 m/s to about 1200 m/s. Such sprayersinclude thermal (e.g., flame sprayers, etc.) and cold sprayers.

Aspects of the present disclosure are directed to thermoplasticformulations that can be tunable, or otherwise have theircharacteristics changed, in real time, during deposition and that caninclude conductive materials, and that can also be conductively tunable.On or more of the first and/or second thermoplastic polymer feedstockcan include at least one conductive material to form a conductivethermoplastic feedstock mixture that can be deposited onto a substratesurface via a high-velocity sprayer to form a tunable conductivethermoplastic first and/or second layer coating on a substrate surface,with the conductive thermoplastic coating having predeterminedcharacteristics. In another aspect, one or more of the first and/orsecond thermoplastic polymer feedstocks may not contain a conductivematerial, and the resulting first and/or second thermoplastic polymerlayers applied to a substrate may not possess electrically resistivecharacteristics.

A thermoplastic polymer feedstock used for a second thermoplasticpolymer layer will be selected to be different from the firstthermoplastic polymer feedstock. According to one present aspect, thesecond thermoplastic polymer feedstock can include at least oneconductive material to form a tunable conductive thermoplastic feedstockmixture that can be deposited via a high-velocity sprayer to form thesecond thermoplastic polymer layer having desired characteristics (e.g.,a desired resistivity, a desired chemical resistance, a desired modulus,a desired robustness, a desired density, etc.). The second thermoplasticpolymer layer is deposited onto the first thermoplastic polymer layerthat has been first (e.g., previously) deposited onto the substratesurface. In a further aspect, the second thermoplastic polymer feedstockmay not contain a conductive material, and the resulting firstthermoplastic polymer layer applied to (e.g., deposited onto) asubstrate surface may not possess electrically resistive characteristics

In further aspects, the first thermoplastic polymer feedstock, and thefirst thermoplastic polymer layer formed and deposited onto a substratesurface, comprise at least one of: a thermoplastic polyester elastomeror a thermoplastic fluoroelastomer. Contemplated thermoplasticelastomers include those that can be obtained as Hytrel® 5526 (DuPont);Dai-El™, (Daikin®); Hipex®, (Kraiburg), etc. When the feedstock is inpowdered form, the first thermoplastic polymer powder feedstockpreferably has an average particle size ranging from about 20 μm toabout 300 μm.

The second thermoplastic polymer feedstock and the second thermoplasticpolymer layer formed, according to present aspects, comprise at leastone of: a nylon, a polyetheretherketone (equivalently referred to asPEEK),a polyetherketoneketone (equivalently referred to as PEKK), apolyamide, a polyphenylsulfide, a polyphenylsulfone, a polysulfone, apolyetheramide, and combinations thereof.

Polyether ether ketone (PEEK) is an organic thermoplastic in thepolyaryletherketone (PAEK) family, with PEEK having the general formula:

PEEK has a coefficient of thermal expansion value (depending upon grade)ranging from of about 20 to about 80 ppm/° F. (i.e. about 2 to about8×10⁻⁵ inlin/° F.), a Young's modulus value of about 3.6 GPa and atensile strength ranging from about 90 MPa to about 100 MPa. PEEK ishighly resistant to thermal degradation as well as attack by bothorganic and aqueous environments (e.g. environments including, withoutlimitation, those environments coming into contact with fuels and fuelsystems, etc.), and has a high resistance to biodegradation.

According to another, and as also presented in the Examples below, retpolymer powder. Polyetherketoneketone (PEKK) is a semi-crystallinethermoplastic in the PAEK family, with PEKK having the general formula:

PEKK has a coefficient of thermal expansion value (depending upon grade)of about 10 to about 20 ppm/° F. (i.e. about 1 to about 2×10⁻⁵ in./in/°F.), a Young's modulus value of about 4.5 GPa and a tensile strength ofabout 102 MPa. PEKK is also highly resistant to thermal degradation aswell as attack by both organic and aqueous environments (e.g.environments including, without limitation, those environments cominginto contact with fuels and fuel systems, etc.), and has a highresistance to biodegradation.

Amorphous and semi crystalline polyamides are commercially availableunder the trade name Trogamid® (Evonik) and include trimethylhexamethylene diamine terephthalic acid and cycloalkiphatic diaminedodecanediodic acid.

Each layer (e.g., the first and second layer) of the multi-layeredsealants disclosed herein can have a different density. Further, eachlayer of the contemplated thermoplastic polymer sealants can be of anydesired thickness, and the multiple layers each can be of the same ordifferent thicknesses. According to one aspect, each layer can bedeposited at a thickness ranging from about 10 μm to about 4000 μm, withthe each differing contemplated layers that together form the presentthermoplastic polymer sealants having a material density ranging fromabout 1.0 g/cc to about 1.8 g/cc.

According to present aspect, the ability to deposit and form athermoplastic polymer coating as a multi-layer coating or sealant on alayer-by-layer process, with each layer having such tailorable,predetermined, and potentially differing characteristics and properties(and deposited to such desired and potentially varying layer-by-layerthicknesses at differing properties, e.g., densities, etc.) can realizesubstantial weight reduction compared with material coatings presentlyused in, for example, aircraft production where overall weight impactsvehicle range, fuel consumption, available cargo capacity, manufacturingtime, etc., all of which can impact total production cost.

If desired, according to further contemplated aspects, the thermoplasticcoatings and sealants (and when conductive components are present toform conductive thermoplastic coatings and sealants, such resultingconductive thermoplastic coatings) can be tailored or “tuned”, forexample, in real time during the coating deposition process, such thatthe deposited coatings possess various desired and predeterminedcharacteristics, e.g., physical, chemical, thermal, etc. Such tunablecharacteristics (e.g. also referred to equivalently herein as“tailorable” characteristics) are.in addition to the desired andtailorable conductivity or resistivity values achievable with thepresently disclosed conductive thermoplastic coatings. This can beachieved by providing differing thermoplastic polymer feedstock(s),differing amounts (e.g., differing comparative ratios, etc.) ofdiffering thermoplastic polymer feedstock(s), additional numbers ofdiffering thermoplastic polymer feedstock(s), by providing additives tothe thermoplastic polymer feedstock(s), etc.

According to other aspects, contemplated conductive feedstock materialsinclude, without limitation, various metallic materials, including,without limitation, metallic powders such as, for example, titanium,nickel alloy, copper, carbon black, graphene powder, or carbonnanotubes. The contemplated conductive feedstock materials, when inpowder form, preferably have an average particle size ranging from about5 μm to about 80 μm.

The thermoplastic polymer feedstock formulations disclosed, according toaspects of the present disclosure, when combined or otherwise mixed withone or more conductive feedstock(s) produce a resulting conductivethermoplastic polymer feedstock mixture that can yield a conductivefirst thermoplastic polymer coating layer formed directly on a substratesurface and/or yield a conductive second thermoplastic polymer layerdeposited on the second thermoplastic polymer layer, with either or bothof the resulting conductive first and/or second thermoplastic polymercoating layers each having a desired and predetermined resistivityranging from about 1×10e⁵ to about 1×10¹¹ ohm-m, and more preferablyfrom about 1×10e⁵ to about 10e⁸ ohm-m.

To provide a conductive thermoplastic coating on a substrate surfacehaving a resistivity ranging from about 1×10e⁵ to about 1×10¹¹ ohm-m,the conductive thermoplastic polymer feedstock(s) preferably have arelative percentage by volume of the conductive component (e.g. theconductive powder) ranging from about 1% to about 9% by volume of thetotal volume of conductive thermoplastic polymer provided to thesprayer.

It is further understood that the thermoplastic polymer feedstockprovided as a feedstock to the high-velocity sprayer can be a mixturethat is formed prior to the introduction of the multi-componentfeedstock to the sprayer. For example, in one aspect, when the feedstockcomprises more than one type of constituent component (e.g., more thanone thermoplastic polymer feedstock; one thermoplastic polymer feedstockand at least one type of conductive feedstock; more than onethermoplastic polymer feedstock and at least one type of conductivepowder feedstock, etc.), the multiple component feedstock materials canbe mixed together to form a thermoplastic (or conductive thermoplastic)polymer mixture, or “feedstock mixture”. The feedstock mixture is thenintroduced as the feedstock to the high-velocity sprayer. For thepurpose of the present disclosure, the term “feedstock” refers to aprecursor material that is supplied from a supply of a material to amixture or is supplied directly to a high-velocity sprayer via a feedline from a supply of a material.

In an alternate aspect, for example, when the feedstock is a powderedfeedstock, and the powdered feedstock comprises more than one type ofpowder component (e.g., more than one thermoplastic polymer powderfeedstock; one thermoplastic polymer powder feedstock and at least oneconductive powder feedstock; more than one thermoplastic polymer powderfeedstock and at least one conductive powder feedstock, etc.), themultiple powdered feedstock components can be directed via separate feedlines to the sprayer, such that no multiple component powdered feedstockmixture is pre-formed as a single feedstock that is then provided to thesprayer. According to this aspect, one or more controllers can be usedto monitor and control the rate at which a single powdered feedstocktype is released from a supply and directed to the sprayer. In this way,the individual flow rate of a particular powdered feedstock component iscontrolled, monitored, and maintained to insure that a particular ratioof feedstock components that arrive at (e.g., are delivered to) thesprayer is achieved and, if desired, maintained for the duration of thematerial (e.g. coating) spray deposition process onto a substratesurface or on to a thermoplastic polymer layer that has already beendeposited onto a substrate surface.

For example, to produce a conductive thermoplastic coating layer havinga resistivity ranging from about 1×10e⁵ to 10e⁸ ohm/m, the presence ofan amount of conductive powder feedstock delivered to the sprayer rangesfrom about 1% to about 9% by volume of the combined powdered materialfeedstock delivered to the sprayer (e.g., the combined powdered materialvolume equaling the volume of thermoplastic polymer powder feedstockcombined with the conductive powder feedstock volume, and, for example,controlled, monitored and maintained by regulating the comparative flowrates of the individual component feedstocks fed via one or more feedlines to the sprayer, etc.).

According to some present aspects, a formed conductive thermoplasticpolymer powder feedstock mixture becomes the thermal sprayer feedstockmaterial that is converted by the high-velocity sprayer (that can, forexample, be a thermal sprayer) into a first and or second conductivethermoplastic polymer coating layer or first or second conductivethermoplastic polymer sealant layer. In the case of the first conductivethermoplastic polymer layer, such first layer is desirably applied (viathe thermal sprayer) directly to a metal, non-metal, or metal/non-metalsubstrate surface. The substrate surface can comprise a substratesurface interface at, for example, a fastener, or a joint. Further, thesubstrate surface can comprise a component or assembly edge, includingedges that require an edge seal.

The tailorable conductive thermoplastic coatings that are obtainedaccording to aspects of the present disclosure provide conductiveflexibility with respect to, for example, dissipating static chargesthat build up with and along a particular material, or are caused bysignificant electrical events including, for example, lightning strikes.In addition, the conductive multi-layered thermoplastic coatings andsealants disclosed herein can have significant advantages over singlelayer conductive thermoplastic coatings and sealants in terms of ease ofhandling, ease of application, safety due to lower toxicity (e.g., ascompared with polysulfides and chromates, etc.), and especially in termsof retention and adhesion characteristics, etc. Further, since thepresently disclosed coatings and sealants are thermoplastic in nature,the multi-layered thermoplastic polymer coatings or sealants do notrequire a separate curing step after application. In other words, themulti-layered thermoplastic polymer coatings/sealants will “set” uponcooling and require no subsequent curing protocol or regimen to “setup”.

Characteristics of the multi-layered thermoplastic polymer coatings andthe discrete thermoplastic polymer coating layers contemplated accordingto present aspects can be altered in a predetermined fashion byproviding a predetermined combination of materials to form a tailoredthermoplastic polymer feedstock material, and by further incorporatingadditives, including, without limitation, additives such as pigments,dyes, or coloring agents, etc. That is, one or more of the disclosedthermoplastic polymer coating layers, each of which, or both of which,or neither of which may be conductive, can be fabricated to furthercomprise a particular color to, for example, facilitate inspection withrespect to both initial application quality as well as rework andmaintenance inspections that will be conducted at various qualitycontrol and servicing intervals. Further, if repair or replacement of athermoplastic polymer coated part or surface (or a conductivethermoplastic polymer coated part or surface) is required, such coatedparts or the coatings on such coated parts can be more easily removedusing various solvent or mechanical removal as compared to, for example,epoxy- or acrylamide-based coatings and/or sealants that require curingregimens.

With respect to adhesion, the first thermoplastic polymer layer that isformed directly onto the substrate surface can be selected to havesuperior adhesion characteristics as compared to the secondthermoplastic polymer layer that will contact the first thermoplasticpolymer layer and will not directly contact the substrate surface.According to one aspect, the first thermoplastic polymer layer displaysadhesion values ranging from about 10 lbs/in to about 30 lbs/in widearea on both metals and non-metals when performing adhesion testing setforth in ASTM D6862-11 (2016) Standard Test Method for 90° PeelResistance, with this protocol for this testing procedure incorporatedby reference herein as if made a part of the present specification. Thefollowing Example is set for as an illustration of how the 90° Peel Testis accomplished according to ASTM D6862-11 (2016) Standard Test Methodfor 90° Peel Resistance, although one skilled in the field of materialscience would readily understand how to perform adhesion testing methodsto satisfy ASTM D6862-11 (2016), and such method in its entirety isincorporated by reference herein as if made a part of the presentapplication.

EXAMPLE

Standard Test Method for 90° Peel Resistance According to ASTM D6862-11(2016)

A test method according to Standard Test Method for 90° Peel Resistanceaccording to ASTM D6862-11 (2016) is conducted to determine theresistance-to-peel strength of an adhesive bond between an aluminumalloy 7075 substrate surface or a carbon fiber reinforced plasticsubstrate surface, and a thermoplastic polymer layer applied to thesubstrate surface. Such first thermoplastic polymer layer is equivalentto the first thermoplastic polymer layer according to aspects of thepresent application and presented herein. A number of samples areproduced having the first thermoplastic polymer layer deposited onto thealuminum or carbon fiber reinforced plastic substrate surface via highvelocity spraying. Samples included the first thermoplastic polymerlayer comprising Hytrel® TPC-ET (DuPont®), Dai-El™ (Daikin®), or Hipex®(Kraiburg). For the Standard Test Method for 90° Peel ResistanceAccording to ASTM D6862-11 (2016), the first thermoplastic polymer layeris deposited onto the substrate surface at a thickness ranging fromabout 0.6 mm to about 1.6 mm.

The sample comprising the adhered first thermoplastic polymer layer ismounted in place onto a 100 Series Modular Universal Test Machine (TestResources, Shakopee, Minn.). A gripper mounted to a moving test loadcell is used to clamp an end of the first thermoplastic polymer coatingin the gripper. The load cell is programmed to move at a constant speedranging from Bout 0.1 mm/sec. to about 10 mm/sec. to move in a upwarddirection away from the substrate surface such that the firstthermoplastic polymer coating is pulled at a maintained angle of 90°relative to the substrate surface. The load cell recorded and sends loadreadings to a readout during the peel testing. Average adhesion valuesof the samples of about 10 lbs/inch wide to about 30 lbs/inch wide arereported.

The thermoplastic coating and sealant systems disclosed herein combinethe benefits of thermoplastic material characteristics withhigh-velocity spray techniques and systems (e.g., thermal flame sprayingand cold spraying), and the deposited thermoplastic coating and sealantcharacteristics are further tailorable to a desired end use as coatingsand/or sealants on a substrate surface. When a conductive powderfeedstock component is added to the thermoplastic powder feedstock, theconductive coatings deposited to a substrate surface have electricalcharacteristics (e.g., conductivity, resistivity, etc.) that can also betailored as required for their intended use as conductive coatings,particularly as coatings and/or sealants on homogeneous or hybridsurfaces comprising metallic and/or non-metallic components.

According to a further aspect, the presently known thermal and coldspray equipment and systems can be retrofitted to deposit coatings madefrom the presently disclosed thermoplastic formulations that can alsoinclude conductive materials to form conductive thermoplastic coatings.Particularly preferred thermal sprayers include flame sprayers.

Thermal spraying techniques are coating processes where melted or heatedmaterials are sprayed onto (e.g., deposited onto) a surface. Feedstockmaterial is supplied to the sprayer as a coating precursor. Thefeedstock is heated by electrical (e.g., plasma or arc) or chemicalmeans (e.g., combustion flame). Thermal spraying can achieve coatingshaving a coating thickness ranging from about 20 μm to about 5.0 mm overa large area and at a high deposition rate as compared to other knowncoating processes, with the presently contemplated deposition rateranging, for example, from about 20 μm on 1 ft² in 10 seconds, orgreater, etc., or coatings deposited at a rate ranging from about 1 toabout 50 grams/second, (g/s), etc.

Flame spray coating refers to a type of thermal spraying where melted orheated feedstock materials are sprayed onto a substrate surface. Thefeedstock (e.g., the coating precursor material) is heated by electrical(e.g., plasma or arc) or chemical means (e.g., combustion flame). Duringcoating processes the substrate preferably undergoes no distortion, asthe substrate temperature remains below about 250° F. during the sprayoperation. When the substrate is metallic, the substrate is notmetallurgically altered. According to present aspects, coating layerthicknesses ranging from about 2 μm to 5.0 mm can be achieved, withdeposition (e.g., coating application) rates for such thicknessesranging from at least about 20 μm on 1 ft² in 10 seconds, or greater; orcoatings deposited at a deposition rate ranging from about 1 to about 50grams/second (g/s), etc.

Without limitation, thermal (e.g., flame, etc.) sprayers andhigh-velocity sprayers useful according to present aspects include, forexample, TAFA Models 5220 HP/HVOF®, 8200 HP/HVOF®, 825 JPid HP/HVOF®(ID), 7780 (UPCC), JP-8000 HP/HVOF®, JP-5000® HP/HVOF® (Praxair, Inc.,Danbury, Conn.); Powderjet® 86, Powderjet® 85 (Metallizing Equipment Co.Pvt. LTD. (Jodhpur, India) Plasma Technology Inc., Torrence, Calif.):and systems available from Plasma Technology Inc. (Torrence Calif.),etc. Universal Flame Spray System PG-550 (Alamo Supply Co., Ltd.,(Houston, Tex.), etc. Various controllers can be used in conjunctionwith the TAFA systems described including, for example, TAFA Model7700GF HVOF System (Praxair, Inc., Danbury, Conn.).

Cold spray processes refer to the thermal spray processes andcollectively refers to processes known as cold gas dynamic spraying,kinetic spraying, high velocity particle consolidation (HPVC), highvelocity powder deposition, supersonic particle/powder deposition (SPD),and the like. In cold spraying, a high velocity gas jet, for example, adeLaval converging/diverging nozzle can be used to accelerate powderparticles generally having an average particle size ranging from about 1μm to about 50 μm. The particles are accelerated by the gas jet at atemperature that is below the melting point of the feedstock materialparticles. The particles are then sprayed onto a substrate that can belocated about 25 mm from the nozzle. The particles impact the substrateand form a coating. Without being bound by a particular theory, it isbelieved that the kinetic energy of the particles, rather than anelevated temperature causes the particles to plastically deform onimpact with the substrate surface to form “splats” that bond together toproduce the coating. The coatings formed from the cold sprayed particlesare formed in the solid state, and not via the melting followed bysolidification as occurs in thermal spray processes (e.g., flamespraying, etc.) using elevated temperature. Such a cold spray processavoids deleterious effects that can be caused by high temperaturedeposition, including, for example, high-temperature oxidation,evaporation, melting, crystallization, residual stress, gas release,etc. As a result, according to present aspects, cold spraying can beadvantageously used for temperature sensitive (e.g., heat sensitive)substrates. The resulting coatings, according to present aspects,possess characteristics including high strength, low porosity andminimal residual stress.

In contrast with the flame sprayer systems mentioned above, in “coldspray” systems powder particles (e.g., feedstock particles) typicallyhaving an average particle size ranging from about 10 μm to about 40 μm,and are accelerated to very high velocities (“high” velocities definedherein velocities ranging from about 200 m/s to 1200 m/s) by asupersonic compressed gas jet at temperatures below their melting point.Upon impact with the substrate, the particles experience extreme andrapid plastic deformation that disrupts the thin surface oxide filmsthat typically are present on metals and alloys. This allows intimateconformal contact between the exposed substrate surfaces under highlocal pressure, permitting bonding to occur with the layers of depositedmaterial. The layers of deposited material can be built up rapidly, withvery high deposition efficiency (e.g., above 90% in some cases). Usingcold spray systems, materials can be deposited without high thermalloads, producing coatings with low porosity and oxygen content. Withoutlimitation, cold sprayers useful according to present aspects include,for example, Impact Spray System 5/8; Impact Spray System 5/11 (ImpactInnovations Waldkraiburg, Germany), etc.

The sprayers used in the systems and methods disclosed herein can beoperated manually, and can also be automated by incorporating orotherwise attaching the sprayer to a robot, or robotic arm that includesor is in communication with sensors, controllers, software and hardware,etc. for the purpose of controlling the operation and movement of thesprayer and the operation of the sprayer during, for example, a materialdeposition (e.g., coating, etc.) cycle. The robot and equipmentassociated with the robot and sprayer can be operated and powereddirectly, and further can be operated remotely in response to, forexample, wireless signals, etc.

Where required coating characteristics included robustness in terms ofadhesion and/or resistance to environmental factors such as thoseencountered, for example, in vehicle fuel tanks, etc., coating materialshave been classified with various toxicities, making their handling andapplication hazardous to personnel. In addition, various applicationsites have been difficult to access. In addition, maintaining and/orreplacing the coatings presently in use has resulted in significantrepair and replacement time, as the removal of cured coatings. Thecoatings made possible according to aspects of the present disclosure,being thermoplastic materials, have significantly reduced toxicityduring application, and can be more easily removed and replaced (e.g.,at scheduled routine inspection and/or replacement).

In addition, at least the presently disclosed first thermoplasticpolymer layer made from the disclosed first thermoplastic polymerformulations maintains adhesion characteristics over a required serviceperiod that is at least equivalent to or exceeds that, which isachievable using the previously available coatings and sealants (e.g.,epoxy- and acrylamide-based options, etc.). The adhesion of the firstthermoplastic polymer layer made from the disclosed first thermoplasticpolymer formulations have an adhesion ranging from about 10 lbs./in toabout 30 lbs./in wide area when performing adhesion testing set forth inASTM D6862-11 (2016) Standard Test Method for 90° Peel Resistance.

Coatings and sealants typically applied to spatially restrictive andother difficult-to-access areas in various assemblies and sub-assemblies(e.g., fuel tanks, etc.) found, for example, in vehicles includingaircraft have required coatings and sealants (e.g., epoxies andacrylamides, etc.) that require significant curing times in excess ofmany days. Further, long curing times delay manufacturing and increasemanufacturing cost. In contrast to epoxy-based and other materialsrequiring curing time of several days or longer, the presently disclosedmulti-layered thermoplastic polymer coatings and sealants appliedaccording to the presently disclosed methods do not require curing, andonly require the time necessary for the thermoplastic material to cooland “set” (e.g. thermoplastic material “set” times understood to rangefrom about less than a few mins. to about several mins., or the amountof time a thermoplastic material takes to cool from an appliedtemperature to about room (ambient) temperature, assuming coatingthicknesses ranging, for example, up to from about 2.5 mm to about 5.0mm). According to present aspects, such “set” times for the depositedthermoplastic polymer coatings and sealants disclosed herein (includingthe deposited conductive thermoplastic polymer coatings and sealants)are in strong contrast to the curing times of several hours or evenseveral days that are required to cure sealants and coatings previouslyused for the purposes intended herein on the substrates and substratesurfaces intended and disclosed herein.

While many of the characteristics of thermoplastic polymers may havebeen desirable for use in coatings and sealants in hard to accesslocations in assemblies and sub-assemblies, use of such thermoplasticpolymeric coatings had been particularly hampered where the coatings orsealants required conductivity (or needed to have certainresistivities), or where it had not been previously possible to deposita thermoplastic coating having variable or tailored characteristics.According to aspects of the present disclosure, the fabrication and useof electrically conductive coatings and sealants that have multiplephysical and chemical characteristics in various discrete layers of amulti-layered thermoplastic polymer sealant material and that cantailored “on demand”, and that are made from presently disclosedthermoplastic polymer formulations, has now been achieved.

FIG. 1 shows a block diagram outlining an aspect showing a thermoplasticpolymer feedstock (that can be a powdered feedstock) and a system 10including directing the thermoplastic polymer feedstock to ahigh-velocity sprayer for depositing a thermoplastic polymer coatingonto a substrate surface. As shown in FIG. 1, a thermoplastic polymerfeedstock 12 is directed from a thermoplastic polymer feedstock supplyvia a thermoplastic polymer powder feedstock feedline 11 incommunication with the thermoplastic polymer feedstock 12 and also incommunication with a high-velocity sprayer 14. Predetermined amounts ofthe thermoplastic polymer feedstock 12 can be directed by any desirablemeans that will direct the thermoplastic polymer feedstock 12 to thehigh-velocity sprayer 14, including automated means regulated by acontroller (not shown) and subject to, for example, software andhardware known to control, for example, feedstock flow rates, etc. Thehigh-velocity sprayer can be a thermal sprayer or a cold sprayer. Asshown in FIG. 1, the thermoplastic polymer feedstock 12 is converted bythe high-velocity sprayer 14 into a thermoplastic polymer coating 16 aonto substrate 16. While the high-velocity sprayer 14 can be operatedmanually, FIG. 1 shows an optional robotic arm 13 (or “robot”) that canbe in communication with a controller 15. Controller 15 can furtheroptionally be in communication with remote or integrated software orhardware, as desired, to control robotic arm movement as well as controlflow rates and amounts of material deposited as a thermoplastic coating16 a onto a substrate 16. Optionally, additional controllers (not shown)can be integrated into system 10 to control one or more aspects ofsystem 10. While the thermoplastic coating 16 a is shown as a singlelayer, it is presently contemplated that the thermoplastic coating 16 ais a first thermoplastic polymer layer applied to the substrate 16, andthat the process can be repeated to deposit a second thermoplasticpolymer layer onto the first thermoplastic polymer layer. The terms“thermoplastic polymer layer” and “thermoplastic polymer coating layer”as used herein are equivalent and interchangeable terms. Further, theterms “thermoplastic coating” and “thermoplastic polymer coating” asused herein are equivalent and interchangeable terms.

FIG. 2A shows a block diagram outlining an aspect showing athermoplastic polymer feedstock mixture (that can be a powderedfeedstock mixture) and system 20 including mixing multiple thermoplasticpolymer feedstocks to form a thermoplastic polymer mixture, and thendirecting an amount of the thermoplastic polymer mixture to ahigh-velocity sprayer and depositing a thermoplastic polymer coatingonto a substrate surface. As shown in FIG. 2A, in system 20,predetermined amounts of a first thermoplastic polymer feedstock 22 a,and a second thermoplastic polymer feedstock 22 b are directed to amixing vessel (not shown). The predetermined amounts of the first andsecond thermoplastic polymer feedstocks 22 a, 22 b are delivered viafirst and second thermoplastic polymer feedstock feedlines 21 a and 21b, respectively, and mixed together to form a thermoplastic polymerfeedstock mixture 27. The thermoplastic polymer feedstock mixture 27 isdirected via feedstock mixture feedline 28 to high-velocity sprayer 24.Feedstock mixture feedline 28, as shown in FIG. 2A, is in communicationwith thermoplastic polymer feedstock mixture 27 and the high-velocitysprayer 24. Predetermined amounts of the first thermoplastic feedstock22 a and the second thermoplastic polymer feedstock 22 b can be directedfrom respective feedstock supplies (not shown) by any desirable means,including automated means regulated by a controller (not shown) andsubject to, for example, software and hardware known to control, forexample, feedstock flow rates from a supply to a sprayer, etc. Thehigh-velocity sprayer 24 can be a thermal sprayer or a cold sprayer. Asshown in FIG. 2A, the thermoplastic polymer feedstock mixture 27 isconverted by the high-velocity sprayer 24 into a thermoplastic polymercoating 26 a deposited onto substrate 26. While the high-velocitysprayer 24 can be operated manually, FIG. 2A shows an optional roboticarm 23 (or “robot”) that can be in communication with a controller 25.Controller 25 can further optionally be in communication with remote orintegrated software or hardware, as desired, to control robotic armmovement as well as control flow rates and amounts of material depositedas a thermoplastic polymer coating 26 a onto a substrate 26. Optionally,additional controllers (not shown) can be integrated into system 20 tocontrol one or more aspects of system 20. According to present aspects,while the thermoplastic polymer coating 26 a is shown as a single layer,it is presently contemplated that the thermoplastic polymer coating 26 ais a first thermoplastic polymer layer applied to the substrate 26, andthat the process can be repeated to deposit a second thermoplasticpolymer layer onto the first thermoplastic polymer layer to form amulti-layered thermoplastic polymer coating.

FIG. 2B shows a block diagram outlining an aspect showing twothermoplastic polymer feedstocks (where one, more than one of thefeedstocks can be in powdered form) and system 30 similar to system 20shown in FIG. 2A, except that, as shown in FIG. 2B, system 30 comprisesfirst and second thermoplastic polymer feedstock feedlines 31 a and 31 bin communication with the high-velocity sprayer 24 and the first andsecond thermoplastic polymer feedstocks 22 a and 22 b, respectively.That is, as shown in FIG. 2B, amounts of the first and secondthermoplastic polymer feedstocks 22 a, 22 b are not mixed together toform a feedstock mixture. Instead, according to the aspect shown in FIG.2B as system 30, a predetermined amount of the first thermoplasticpolymer feedstock 22 a is directed to high-velocity sprayer 24 via firstthermoplastic polymer feedstock feedline 31 a. Similarly, apredetermined amount of the second thermoplastic polymer feedstock 22 bis directed to the high-velocity sprayer 24 via second thermoplasticpolymer feedstock feedline 31 b. While the high-velocity sprayer 24 canbe operated manually, FIG. 2B shows an optional robotic arm 23 (or“robot”) that can be in communication with a controller 25. Controller25 can further optionally be in communication with remote or integratedsoftware or hardware, as desired, to control robotic arm movement aswell as control flow rates and amounts of material deposited as athermoplastic polymer coating 26 a onto a substrate 26. Optionally,additional controllers (not shown) can be integrated into system 30 tocontrol one or more aspects of system 30. While the thermoplasticcoating 26 a is shown in FIGS. 2A and 2B as a single layer, it ispresently contemplated that the thermoplastic coating 26 a is a firstthermoplastic polymer layer applied to the substrate 26, and that theprocess can be repeated to deposit a second thermoplastic polymer layeronto the first thermoplastic polymer layer to form a multi-layeredcoating

FIG. 3A shows a block diagram outlining an aspect showing athermoplastic polymer feedstock and a conductive feedstock (where eitheror both of the feedstocks can be in powdered form) and a system 40. Asshown in FIG. 3A, in system 40, a thermoplastic polymer feedstock 42 a,and a conductive feedstock 42 b are directed to a mixing vessel (notshown). The predetermined amounts of the first and second thermoplasticpolymer feedstocks 42 a, 42 b are delivered via first and secondthermoplastic polymer feedstock feedlines 41 a and 41 b, respectively,and mixed together to form a conductive thermoplastic polymer feedstockmixture 47. An amount of the conductive thermoplastic polymer feedstockmixture 47 is directed via conductive thermoplastic polymer feedstockmixture feedline 48 to high-velocity sprayer 44. Feedline 48 as shown inFIG. 3A is in communication with conductive thermoplastic feedstockmixture 47 and the high-velocity sprayer 44. Predetermined amounts ofconductive thermoplastic polymer feedstock mixture 47 can be directed tothe high-velocity sprayer 44 by any desirable means, including automatedmeans regulated by a controller (not shown) and subject to, for example,software and hardware known to control, for example, feedstock flowrates from a supply to a sprayer, etc. The high-velocity sprayer 44 canbe a thermal sprayer or a cold sprayer. As shown in FIG. 3A, theconductive thermoplastic polymer feedstock is converted by thehigh-velocity sprayer 44 into a conductive thermoplastic polymer coating46 a deposited onto substrate 46. While the high-velocity sprayer 44 canbe operated manually, FIG. 3A shows an optional robotic arm 43 (or“robot”) that can be in communication with a controller 45. Controller45 can further optionally be in communication with remote or integratedsoftware or hardware, as desired, to control movement of the robotic arm43 as well as control flow rates and amounts of deposited conductivethermoplastic polymer coating 46 a onto a substrate 46. Optionally,additional controllers (not shown) can be integrated into system 40 tocontrol one or more aspects of system 40.

FIG. 3B shows a block diagram outlining an aspect showing a conductivethermoplastic polymer (that can be in powdered form) and a system 50similar to system 40 shown in FIG. 3A, except that as shown in FIG. 3B,system 50 comprises a thermoplastic polymer feedstock feedline 51 a incommunication with a thermoplastic polymer feedstock 42 a and ahigh-velocity sprayer 44. Conductive feedstock feedline 51 b is shown incommunication with the conductive feedstock 42 b and the high-velocitysprayer 44. That is, as shown in FIG. 3B, an amount of the thermoplasticpolymer feedstock 42 a is not mixed with an amount of the conductivefeedstock 42 b to form a conductive thermoplastic polymer feedstockmixture. Instead, according to an aspect shown in FIG. 3B as system 50,a predetermined amount of the thermoplastic polymer feedstock 42 a isdirected to high-velocity sprayer 44 via thermoplastic polymer feedstockfeedline 51 a. Similarly, a predetermined amount of the conductivefeedstock 42 b is directed to the high-velocity sprayer 24 viaconductive feedstock feedline 51 b. While the high-velocity sprayer 44can be operated manually, FIG. 3B shows an optional robotic arm 43 (or“robot”) that can be in communication with a controller 45. Controller45 can further optionally be in communication with remote or integratedsoftware or hardware, as desired, to control movement of the robotic arm43 as well as control flow rates and amounts of deposited conductivethermoplastic polymer coating 46 a onto a substrate 46. Optionally,additional controllers (not shown) can be integrated into system 50 tocontrol one or more aspects of system 50. According to present aspects,while the thermoplastic polymer coating 46 a is shown as a single layer,it is presently contemplated that the thermoplastic polymer coating 46 ais a first thermoplastic polymer layer applied to the substrate 46, andthat the process can be repeated to deposit a second thermoplasticpolymer layer onto the first thermoplastic polymer layer to form amulti-layered thermoplastic polymer coating.

FIG. 4A shows a block diagram outlining an aspect showing a conductivethermoplastic polymer feedstock (that can be a powdered feedstock) and asystem 60 including mixing first and second thermoplastic polymerfeedstocks with a conductive feedstock to form a conductivethermoplastic feedstock mixture, and then directing an amount of theconductive thermoplastic feedstock mixture to a high-velocity sprayerand depositing a conductive thermoplastic polymer coating onto asubstrate surface. Any or all of the feedstocks can be in powdered form.As shown in FIG. 4A, in system 60, an amount of a first thermoplasticpolymer feedstock 62 a, an amount of a second thermoplastic polymerfeedstock 62 b, and an amount of a conductive feedstock 62 c aredirected to a mixing vessel (not shown) and are mixed together to form aconductive thermoplastic polymer feedstock mixture 67. A desired amountof the conductive thermoplastic polymer feedstock mixture 67 is directedvia feedstock mixture feedline 68 to high-velocity sprayer 64. Feedstockmixture feedline 68, as shown in FIG. 4A, is in communication withconductive thermoplastic polymer feedstock mixture 67 and thehigh-velocity sprayer 64. Predetermined amounts of: 1) the firstthermoplastic polymer feedstock 62 a; 2) the second thermoplasticpolymer feedstock 62 b; and 3) the conductive feedstock 62 c aredirected to the conductive thermoplastic polymer feedstock mixture 67via first thermoplastic polymer feedstock feedline 61 a, secondthermoplastic polymer feedstock feedline 61 b and conductive polymerfeedstock feedline 61 c, respectively, by any desirable means.Predetermined amounts of conductive thermoplastic polymer feedstockmixture 67 are directed to the high-velocity sprayer 64 by any desirablemeans, including, for example, an automated means regulated by acontroller (not shown) and subject to, for example, software andhardware known to control, for example, feedstock flow rates to asprayer, etc. The high-velocity sprayer 64 can be a thermal sprayer or acold sprayer. As shown in FIG. 4A, the conductive thermoplastic polymerfeedstock mixture 67 is converted by the high-velocity sprayer 44 into aconductive thermoplastic polymer coating 66 a deposited onto substrate46. While the high-velocity sprayer 64 can be operated manually, FIG. 4Ashows an optional robotic arm 63 (or “robot”) that can be incommunication with a controller 65. Controller 65 can further optionallybe in communication with remote or integrated software or hardware, asdesired, to control movement of the robotic arm 63 as well as controlflow rates and amounts of deposited conductive thermoplastic polymercoating 66 a onto a substrate 66. Optionally, additional controllers(not shown) can be integrated into system 60 to control one or moreaspects of system 60.

FIG. 4B shows a block diagram outlining an aspect showing a conductivethermoplastic polymer and a system 70 similar to system 60 shown in FIG.4A, except that as shown in FIG. 4B, system 70 comprises: 1) a firstthermoplastic polymer feedstock feedline 71 a in communication with thefirst thermoplastic polymer feedstock 62 a and the high-velocity sprayer64; 2) a second thermoplastic polymer feedstock feedline 71 b incommunication with the first thermoplastic polymer feedstock 62 b andthe high-velocity sprayer 64; and 3) a conductive feedstock feedline 71c in communication with the conductive feedstock 62 c and thehigh-velocity sprayer 64. That is, as shown in FIG. 4B, an amount of thefirst thermoplastic polymer feedstock 62 a, and an amount of the secondthermoplastic polymer feedstock 62 b are not mixed with an amount of theconductive feedstock to form a conductive thermoplastic polymerfeedstock mixture. Instead, according to system 70 shown in FIG. 4B, apredetermined amount of the first thermoplastic polymer feedstock 62 ais directed to high-velocity sprayer 64 via first thermoplastic polymerfeedstock feedline 71 a. Similarly, a predetermined amount of the secondthermoplastic polymer feedstock 62 b is directed to high-velocitysprayer 64 via second thermoplastic polymer feedstock feedline 71 b.Further, a predetermined amount of the conductive feedstock 62 c isdirected to the high-velocity sprayer 64 via conductive feedstockfeedline 71 c. Any of the feedstocks can be in powdered form. While thehigh-velocity sprayer 64 can be operated manually, FIG. 4B shows anoptional robotic arm 63 that can be in communication with a controller65. Controller 65 can further optionally be in communication with remoteor integrated software or hardware, as desired, to control movement of arobotic arm 63 (or “robot”) as well as control flow rates and amounts ofdeposited conductive thermoplastic polymer coating 66 a onto a substrate66. Optionally, additional controllers (not shown) can be integratedinto system 70 to control one or more aspects of system 70. While thethermoplastic coating 66 a is shown as a single layer, it is presentlycontemplated that the thermoplastic coating 66 a is a firstthermoplastic polymer layer applied to the substrate 66, and that theprocess can be repeated to deposit a second thermoplastic polymer layeronto the first thermoplastic polymer layer to form a multi-layeredcoating.

The robotic arm disclosed above is equivalently referred to herein as a“robot”, such that any feature of the robot (in addition to the “arm”)can control the relative movement of the high-velocity sprayer, and/orthe robot can control the direction of spray emitted from thehigh-velocity sprayer (e.g., the robot controls the direction and changethe direction of spray from the high-velocity sprayer while the sprayeritself remains in a substantially stationary position, etc.).

FIG. 5 is an illustration of a vehicle in the form of an aircraft 80,with the aircraft 80 comprising assemblies and sub-assemblies andcomponents that further comprise fasteners, with the fasteners havingcoatings according to aspects of the present disclosure, with thefasteners coated using systems and coated via methods according toaspects of the present disclosure. It is further understood that, thecoatings described herein can be advantageously coated onto substratesoccurring on components, including substrate interfaces and edgesrequiring the application of sealant material to achieve various typesof seals (e.g., filet seals, edge seals, etc.) in assemblies andsub-assemblies incorporated in further types of manned and unmannedaircraft, terrestrial vehicles, sub-surface and surface marine (e.g.,water borne) vehicles, manned and unmanned satellites, etc.

FIGS. 6A, 6B, 7A, 7B, 8A, and 8B are flowcharts outlining aspects of thepresent disclosure. FIG. 6A outlines a method 100 a comprising directing102 a at least one thermoplastic polymer (e.g. a thermoplastic polymerfeedstock that can be in powdered form) to a high-velocity sprayer,followed by forming 104 a a first thermoplastic polymer sprayformulation at or near the high-velocity sprayer. The method outlined inFIG. 6A further comprises directing 106 a the first thermoplastic sprayformulation from the high-velocity sprayer to a substrate having asubstrate surface, and forming 108 a a first thermoplastic polymercoating layer on the substrate surface. The method outlined in FIG. 6Ais understood to at least relate to the systems shown in FIGS. 1, 2A,and 2B.

FIG. 6B outlines a method 100 b comprising directing 102 b at least onethermoplastic polymer (e.g. a thermoplastic polymer feedstock that canbe in a powdered form) to a high-velocity sprayer, followed by forming104 b a second thermoplastic polymer spray formulation at or near thehigh-velocity sprayer. The method outlined in FIG. 6B further comprisesdirecting 106 b the second thermoplastic spray formulation from thehigh-velocity sprayer to a substrate having a substrate surface andforming 108 b a second thermoplastic polymer coating on the firstthermoplastic polymer coating layer. The method outlined in FIG. 6B isunderstood to at least relate to the systems shown in FIGS. 1, 2A, and2B.

FIG. 7A outlines a method 110 comprising directing 102 a an amount of atleast one first thermoplastic polymer (e.g. a thermoplastic polymerfeedstock in a powdered form) to a high-velocity sprayer, followed bydirecting 103 a an amount of conductive material to the high-velocitysprayer concurrently with the thermoplastic polymer and forming 104 c aconductive first thermoplastic polymer spray formulation at or near thehigh velocity sprayer. The method further comprises directing 106 c theconductive first thermoplastic polymer spray formulation from thesprayer to a substrate surface, and forming 108 c a conductive firstthermoplastic coating on the substrate surface. The method outlined inFIG. 7A is understood to at least relate to the systems shown in FIGS.3A, 3B, 4A, and 4B.

FIG. 7B outlines a method 112 comprising directing 102 b an amount of atleast one first thermoplastic polymer (e.g. a thermoplastic polymerfeedstock in a powdered form) to a high-velocity sprayer, followed bydirecting 103 b an amount of conductive material to the high-velocitysprayer concurrently with the thermoplastic polymer and forming 104 d aconductive second thermoplastic polymer spray formulation at or near thehigh velocity sprayer. The method further comprises directing 106 d theconductive second thermoplastic polymer spray formulation from thesprayer to the conductive first thermoplastic polymer coating layer, andforming 108 d a conductive second thermoplastic coating layer on theconductive first thermoplastic polymer coating layer. The methodoutlined in FIG. 7B is understood to at least relate to the systemsshown in FIGS. 3A, 3B, 4A, and 4B.

FIG. 8A outlines a method 120 comprising directing 102 c an combinedamount of a first thermoplastic polymer and an amount of a secondthermoplastic polymer in a mixture to a high-velocity sprayer (e.g. acombined first and second thermoplastic polymer feedstock that can be ina powdered form), followed by directing 103 c an amount of conductivematerial to the high-velocity sprayer concurrently with the combinedthermoplastic polymer mixture and forming 104 c a conductive firstthermoplastic polymer spray formulation. The method further comprisesdirecting 106 c the conductive first thermoplastic polymer formulationfrom the sprayer to a substrate surface and forming 108 c a conductivefirst thermoplastic coating on the substrate surface. The methodoutlined in FIG. 8A is understood to at least relate to the systemsshown in FIGS. 4A, and 4B.

FIG. 8B outlines a method 125 comprising directing 102 d an combinedamount of a first thermoplastic polymer and an amount of a secondthermoplastic polymer in a mixture to a high-velocity sprayer (e.g. acombined first and second thermoplastic polymer feedstock that can be ina powdered form), followed by directing 103 d an amount of conductivematerial to the high-velocity sprayer concurrently with the combinedthermoplastic polymer mixture and forming 104 d a conductive secondthermoplastic polymer spray formulation. The method further comprisesdirecting 106 d the conductive second thermoplastic polymer formulationfrom the sprayer to the conductive first thermoplastic polymer coatinglayer, and forming 108 d a conductive second thermoplastic polymercoating layer on the conductive first thermoplastic polymer coatinglayer. The method outlined in FIG. 8A is understood to at least relateto the systems shown in FIGS. 4A, and 4B.

FIG. 9 shows a representative illustration of a thermal spray depositionsystem 130 according to aspects of the present disclosure. As shown inFIG. 9, a feedstock 132 comprising individual feedstock particles 133are heated, such as by directing the feedstock particles 133 to a flame134 in a thermal sprayer (e.g., a flame sprayer, not shown in FIG. 9) ata particular velocity and in a direction as indicated by horizontalarrows. The feedstock particles 133 deform as they melt to a semi-solidor liquid state. The deformed particles 135 then impact a substratesurface 136. The deformed particles continue to impact the substratesurface 136. As the illustrated thermal spray deposition processcontinues, a deposited layer 138 forms on the substrate surface 136.

FIG. 10 is an illustration of a high velocity spray process 140 that caninclude the use of a high-velocity flame sprayer or a high-velocity coldsprayer (collectively and equivalently referred to as the “sprayer” orthe “high-velocity sprayer”). As shown in FIG. 10, and according toaspects of the present disclosure, a sprayer 142 is operated to emit anddirect a thermoplastic polymer particulate spray 143 formed byprocessing thermoplastic polymer feedstock (that can be a powderedfeedstock) that is directed to the sprayer. The feedstock can betailored and can be made into a conductive feedstock (that can also betailored) by adding varying amounts of conductive feedstock (that can bein a powdered form) to the thermoplastic polymer feedstock (that canalso be in powdered form). The thermoplastic polymer particulate spray143 is directed from the sprayer 142 to a fastener 144 installed into asubstrate 146. At least one thermoplastic polymer feedstock acts as afeedstock supply (not shown) that is supplied to the sprayer 142.

According to further aspects, the feedstock can also be a conductivethermoplastic polymer powder feedstock mixture, with the feedstockmixture comprising a conductive powder feedstock. According to furtheraspects, when the feedstock comprises multiple components, eachcomponent can alternatively be supplied individually and alsosubstantially concurrently to the sprayer via discrete feedstockfeedlines (not shown). If desired, the predetermined amounts of multiplefeedstock components can be delivered to the sprayer via one or morefeedstock feedlines by a sequencer and/or controller driven byautomatically or manually in conjunction with attendant software andhardware, including the use of a robot. In this way the fastener 144 iscoated to a predetermined thickness as particles in the particulatespray impact the fastener 144, the substrate 146, and thefastener/substrate interface 147. As shown in FIG. 10, the fastener 144can be made from a metal or non-metal and the substrate 146 can also bemade from a metal or a non-metal.

According to aspects of the present disclosure, when at least one of afastener and the substrate are made from a metal having a differentelectrical resistivity (or electrical conductivity), a thermoplasticpolymer feedstock can be “doped” with a predetermined amount ofconductive feedstock to form a conductive thermoplastic polymerfeedstock. The feedstock can be in a powdered form. As the conductivethermoplastic feedstock proceeds into and through the high-velocitysprayer, the conductive thermoplastic polymer feedstock comprisingconductive feedstock particles and thermoplastic polymer feedstockparticles is subjected at the sprayer to heat and/or high velocity viagas jets to at least soften and deform the particles in the conductivethermoplastic polymer feedstock. The combined feedstock particles leavethe sprayer as a conductive thermoplastic polymer particulate spray at apredetermined velocity and impact a desired target such as, for example,the fastener 144, substrate 146 and the fastener/substrate interface 147as shown in FIG. 10.

Upon impact on the selected target(s), the particulate spray forms afirst thermoplastic polymer coating on the target(s) (e.g., substratesurface(s), etc.) with, if desired, the first thermoplastic polymercoating having a desired, predetermined, and tailorable resistivityvalue. Further, the resistivity value of the first thermoplastic polymercoating formed on the substrate surface can be tailored or “tuned” to aparticular resistivity value. According to present aspects describedabove, the coating process is substantially repeated to deposit a secondthermoplastic polymer coating layer, then can also be conductive, ontothe first thermoplastic polymer layer, with the two deposited layerscomprising a composition different from one another.

If the coated materials are subjected to an electromagnetic effect(EME), such as, for example, from the electrical discharge of staticelectricity, or a from a lightning strike, the conductivity of themulti-layer thermoplastic coating will at least ameliorate deleteriouseffects from the EME that would otherwise be encountered at or near thefastener or at or near the fastener/substrate interface (e.g., adjoinedstructures) due to dissimilar resistivity values of such adjoined and/orproximately positioned structures. The multi-layer thermoplasticcoatings made possible according to aspects of the present disclosurefurther obviate the need to stock and employ expensive alternativesincluding, for example, physically applied fastener caps that areexpensive and time-consuming to install, maintain, and replace.

FIG. 11 is an illustration of an assembly comprising two structuresadjoined via fastening with fasteners. As shown in FIG. 11, an assembly150 comprises a first substrate 152 having a first substrate surfaceadjoined to a second substrate 153 having a second substrate surface.Fasteners 154 are shown fitted, for example, through aligned holes (notshown) in substrates 152, 153, such that, the fasteners, when secured,exert pressure sufficient to hold substrates 152, 153 together in anadjoined orientation. As further shown in FIG. 11, fasteners 154 have afastener first end 154 a contacting a surface (the “upper” surface) ofsubstrate 152, and a fastener second end 154 b contacting a surface (the“lower” surface) of substrate 153.

FIG. 12 is a cross-sectional side-view of a coated fastener in positionfastening together two substrates. As shown in FIG. 12, a fastenerassembly 160 comprises first and second substrates, 162 and 163respectively, fastened together by fastener 164. As shown in FIG. 12,the fastener 164, along with portions of substrates 162, 163 includingfastener/substrate interfaces 166 a, 166 b, 166 c and 166 d, are coatedby a sealant 168 that is formed by the deposition of two thermoplasticpolymer layers; namely first thermoplastic polymer coating layer 168 a,and second thermoplastic polymer coating layer 168 b. Firstthermoplastic polymer coating layer 168 a is shown contacting fastener164 and at least a portion of first substrate 162 and at least a portionof second substrate 163. First thermoplastic polymer coating layer 168 ais shown covered by a second thermoplastic polymer coating layer 168 b.Though shown in FIG. 12 as individual points, the fastener/substrateinterface is understood to represent a “perimeter”, or an “area”, suchas, for example (and as shown in FIG. 12), a substantially circularperimeter located at the fastener/substrate interface. The terms“thermoplastic polymer layer” and “thermoplastic polymer coating layer”as used herein are equivalent and interchangeable terms.

First and second thermoplastic polymer coating layers 168 a, 168 b (andthe feedstocks used to form the two thermoplastic polymer coatinglayers) are selected to deliver predetermined characteristics to thetwo-layer coating sealant. For example, in the two-layer sealant of thepresent application, the first thermoplastic polymer that forms thefirst thermoplastic polymer coating layer, and that is depositeddirectly onto a substrate, can be selected for its superior adhesioncharacteristics, while the second thermoplastic polymer material thatforms the second thermoplastic polymer coating layer, and that isdeposited onto the first thermoplastic polymer coating layer need nothave adhesion characteristics that are equivalent to the first coatinglayer, since the second coating layer will not be adhering to thesubstrate.

A further aspect discloses an assembly comprising a first substrate anda second substrate, with the first and second substrates locatedproximate to one another, and a two-layer thermoplastic polymer sealantlocated on at least one of the first and second substrates. The sealantcan comprise a first thermoplastic polymer layer with adhesionproperties ranging from about 10 lbs/in to about 30 lbs/in wide areafrom a 90° peel test when performing adhesion testing set forth in ASTMD6862-11 (2016) Standard Test Method for 90° Peel Resistance.

For example, and according to another present aspect, the firstthermoplastic polymer coating layer that is deposited onto the substratesurface can be made from a first thermoplastic polymer material that hassuperior adhesion characteristics, modulus characteristics etc.According to present aspects, the first thermoplastic polymer coatinglayer can comprise a modulus value of less than 1000 MPa having anelongation at break greater than 100%, while, for example, the secondthermoplastic polymer layer can be selected because such secondthermoplastic polymer material, from which the second coating layer ismade, has modulus of less than about 4 MPa with an elongation at breakof greater than about 20%.

In addition, the two-layer sealant that is deposited on, for example, anassembly, component, etc., may need to encounter or otherwise exist in aharsh environment (e.g., exposure to volatiles or other chemicals, suchas, for example, fuel in a fuel tank, etc.). In this aspect, the secondthermoplastic polymer material that forms the second thermoplasticpolymer coating layer of the two-layer sealant (and that is exposed tothe environment as the outermost coating layer of the two-layer sealant)can be selected to take advantage of chemical resistance characteristicsthat the first layer of the two-layer sealant does not possess.

For example, and according to a present aspect, the second thermoplasticpolymer coating layer that is deposited onto the first thermoplasticpolymer coating layer can be made from a second thermoplastic polymermaterial that has superior chemical resistance characteristics, moduluscharacteristics etc. According to present aspects, if, for example, thetwo-layer sealant is deposited onto a component or assembly such as, forexample, an aircraft fuel tank interior component or assembly, etc., thesecond thermoplastic polymer coating layer can be made from a secondthermoplastic polymer material that has a chemical resistance to long orshort term exposure to, for example, jet fuel, hydraulic liquids, othervolatile materials, etc. with the chemical resistance/exposure measuredin terms of the second thermoplastic polymer material (and secondthermoplastic polymer coating layer) incurring less than 10% weightgain, and/or less than a 10% reduction in a desired mechanical property,etc.

According to aspects of the present disclosure, at least the first orsecond thermoplastic polymer coating layer can be conductive, with oneor both of the first and/or second thermoplastic polymer coating layershaving a desired and/or predetermined and tailorable (e.g., “tunable”)resistivity. It is understood that the EME effects that are dissipatedby conductive thermoplastic polymer coating layers would be dissipatedby the second thermoplastic polymer coating layer that is oriented“uppermost” or otherwise serves as the outer coating layer of thetwo-layer sealant. According to further aspects, the substrates 162, 163can be made from a metal or non-metal material. Fastener 164 can be madefrom metal or non-metal material. Each of substrates 162, 163 and/orfastener 164 can be made from the same or different metals or the sameor different non-metals. If the resistivity value of substrates 162, 163differ from each other and/or differ from the resistivity value of thefastener 164, the fastening assembly area or region can be susceptibleto deleterious effects when confronted with an EME event (e.g., such asfrom static discharge or a lightning strike, etc.).

According to present aspects, the resistivity value of the first and/orsecond thermoplastic polymer coating layers (168 a, 168 b respectively)formed to cover the fastener 164 can be tailored or “tuned” to anyresistivity value as desired, and preferably ranging from about 1×10⁵ toabout 1×10¹¹ ohm-m, and more preferably ranging from about 1×10⁵ toabout 1×10⁸ ohm-m. If the coating materials and/or the underlyingsubstrate material are subjected to an electromagnetic effect (EME),such as, for example, from the electrical discharge of staticelectricity, or a from a lightning strike, the conductivity of thethermoplastic coating layers comprising the two-layer thermoplasticpolymer sealant disclosed herein will at least ameliorate deleteriouseffects from the EME that would otherwise be encountered at or near thefastener or at or near the fastener/substrate interface (e.g., adjoinedstructures) due to dissimilar resistivity values of such adjoined and/orproximately positioned structures.

FIG. 13 is an overhead perspective view, or “top” view of a coatedfastener according to aspects of the present disclosure. As shown inFIG. 13, an area of an assembly 170 comprises a fastener 172 installedin a substrate 174. A two-layer thermoplastic polymer coating sealant176 is shown coating a portion of substrate 174 and fastener 172 to forma two-layer thermoplastic polymer coated fastener 178, also referred toequivalently herein as a “thermoplastic polymer sealed fastener”. Aswith the fastener 164 shown in FIG. 12, at least one layer of thetwo-layer thermoplastic polymer sealant (equivalently referred to as a“two-layer thermoplastic polymer coating sealant” or a multi-layerthermoplastic polymer coating sealant”) can comprise a conductivematerial to form a two-layer conductive thermoplastic polymer coating onthe fastener and at least a portion of the substrate.

According to present aspects, the resistivity value of the conductivethermoplastic polymer coating layer formed to cover the fastener (e.g.,the first thermoplastic polymer coating layer) or the secondthermoplastic polymer coating layer that covers the first thermoplasticcoating layer can be tailored or “tuned” to a predetermined resistivityvalue such that, if the coated materials are subjected to anelectromagnetic effect (EME), such as, for example, from the electricaldischarge of static electricity, or a from a lightning strike, theconductivity of the thermoplastic coating will at least amelioratedeleterious effects from the EME that would otherwise be encountered ator near the fastener or at or near the fastener/substrate interface(e.g., adjoined structures) due to dissimilar resistivity values of suchadjoined and/or proximately positioned structures.

FIG. 14A is a flowchart outlining methods according to aspects of thepresent disclosure. As shown in FIG. 14A, according to presentlydisclosed aspects, the first steps of a method 200 for coating aninstalled fastener includes delivering 202 a a first thermoplasticpolymer feedstock, that can be a powdered feedstock, to a high-velocitysprayer. The high-velocity sprayer is preferably a high-velocity sprayerthat can be a thermal sprayer (e.g. flame sprayer) or a cold sprayer.Further contemplated steps of method 200, include forming 204 a a firstthermoplastic polymer coating material followed by directing 206 a thefirst thermoplastic polymer coating material from the high-velocitysprayer to a fastener and fastener/substrate interface on substratesurface, and depositing 208 a an amount of the first thermoplasticpolymer coating material on the fastener to form a first thermoplasticpolymer coating layer on the fastener and at the fastener/substrateinterface, and coating 210 a the fastener with the first thermoplasticpolymer coating layer. The methods outlined in FIG. 14A can be used toaccomplish the coating methods to prepare the coated fasteners,fastener/substrate interfaces and substrates shown and/or described inone or more of FIG. 1 through FIG. 13.

FIG. 14B is a flowchart outlining methods according to aspects of thepresent disclosure. As shown in FIG. 14B, according to presentlydisclosed aspects, further steps (e.g., steps subsequent to the stepspresented as method 200 in FIG. 14A) are shown as method 201 deliveringa second thermoplastic polymer coating layer onto the firstthermoplastic polymer coating layer. As shown in FIG. 14B, method 200further includes delivering 202 b a second thermoplastic polymerfeedstock, that can be a powdered feedstock, to a high-velocity sprayer.The high-velocity sprayer is preferably a high-velocity sprayer that canbe a thermal sprayer (e.g. flame sprayer) or a cold sprayer. Furthercontemplated steps of method 200, include forming 204 b a secondthermoplastic polymer coating material followed by directing 206 b thesecond thermoplastic polymer coating material from the high-velocitysprayer to a fastener and fastener/substrate interface on substratesurface, and depositing 208 b an amount of the second thermoplasticpolymer coating material onto the first thermoplastic polymer coatinglayer previously deposited onto the fastener and fastener/substrateinterface, to form a second thermoplastic polymer coating layer on thefirst thermoplastic polymer coating layer, and coating 210 b the firstthermoplastic polymer coating layer with the second thermoplasticpolymer coating layer. The methods outlined in FIG. 14B can be used toaccomplish the coating methods to prepare the coated fasteners,fastener/substrate interfaces and substrates shown and/or described inone or more of FIG. 1 through FIG. 13.

When a fastener, including a metal fastener, is installed into anassembly that, for example, includes fastened first and second parts orsubstrates, and at least one substrate is made from a metal, accordingto the present disclosure, the thermoplastic coating material isconductive, and in certain aspects the conductive coating has aresistivity ranging from about 10⁵ to 18¹ ohm-m. FIG. 15A is a flowchartoutlining methods according to aspects of the present disclosure. Asshown in FIG. 15A, according to presently disclosed aspects, a method300 for coating an installed fastener includes delivering 302 a aconductive first thermoplastic polymer that can be in a powdered form,to a high-velocity sprayer. The high-velocity sprayer is preferably ahigh-velocity sprayer that can be a thermal sprayer (e.g. flame sprayer)or a cold sprayer. Further contemplated steps of method 300, includeforming 304 a a conductive first thermoplastic polymer coating materialfollowed by directing 306 a the conductive first thermoplastic polymercoating material from the sprayer to a fastener and fastener/substrateinterface on substrate surface, and depositing 308 a an amount of theconductive first thermoplastic polymer coating material on the fastenerto form a conductive first thermoplastic polymer coating layer on thefastener and at the fastener/substrate interface, and coating 310 a thefastener with the conductive first thermoplastic polymer coating layer.The methods outlined in FIG. 15A can be used to accomplish the coatingmethods to prepare the coated fasteners, fastener/substrate interfacesand substrates shown and/or described in one or more of FIG. 1 throughFIG. 14B.

FIG. 15B is a flowchart outlining methods according to aspects of thepresent disclosure. As shown in FIG. 15B, according to presentlydisclosed aspects, further steps (e.g., steps subsequent to the stepspresented as method 300 in FIG. 15A) are shown as method 300 comprisingdelivering a second thermoplastic polymer coating layer onto the firstthermoplastic polymer coating layer. As shown in FIG. 15B, according topresently further disclosed aspects, the method 300 for coating aninstalled fastener further includes delivering 302 b a conductive secondthermoplastic polymer that can be in a powdered form, to a high-velocitysprayer. The high-velocity sprayer is preferably a high-velocity sprayerthat can be a thermal sprayer (e.g. flame sprayer) or a cold sprayer.Further contemplated steps of method 300 include forming 304 b aconductive second thermoplastic polymer coating material followed bydirecting 306 b the conductive second thermoplastic polymer coatingmaterial from the sprayer to the fastener and fastener/substrateinterface on substrate surface, and depositing 308 b an amount of theconductive second thermoplastic polymer coating material on theconductive first thermoplastic polymer coating layer to form aconductive second thermoplastic polymer coating layer on the fastenerand at the fastener/substrate interface, and coating 310 b theconductive first thermoplastic polymer coating layer with the conductivefirst thermoplastic polymer coating layer. The methods outlined in FIG.15B can be used to accomplish the coating methods to prepare the coatedfasteners, fastener/substrate interfaces and substrates shown and/ordescribed in one or more of FIG. 1 through FIG. 15A. As statedpreviously herein. If desired, the methods outlined in the present FiGs.can be modified such that one or more of the first and/or secondthermoplastic polymer coating layers are conductive and can have theirdegree of conductivity “tuned” to a desired degree by appropriatelydoping the thermoplastic polymer feedstock with varying andpredetermined amounts of conductive material.

The characteristics of the presently disclosed two-layer thermoplasticpolymer coatings are particularly desirable for use as two-layercoatings and two-layer sealants (in coating and sealing processes) forsubstrates, components, assemblies, etc. in hard to access locations inassemblies and sub-assemblies. Such substrates include substratesrequiring or otherwise benefitting from the use of thermoplastic polymercoatings and sealants having a predetermined and tailorable conductivity(or resistivity, etc.), or assembly locations where it had not beenpreviously possible to deposit a coating or sealant having variable ortailored conductive or other characteristics. According to aspects ofthe present disclosure, the fabrication and use of electrically variableconductive coatings and sealants that can also have multiple physicaland chemical characteristics tailored, and that are made from presentlydisclosed thermoplastic polymer formulations, and applied according topresently disclosed methods, has now been achieved.

According to present aspects, the two-layer coating approach allows forimproved and tailorable or tunable overall characteristics of theoverall coating (e.g., the two or multiple layer coating). In otherwords, if a particular adhesion level or other characteristic isdifficult to incorporate into a coating where certain othercharacteristics are desirable (e.g. a particular outer modulus, outerconductivity or resistivity, etc.) the inner portion of the coatingrequiring a heightened adhesion, for example can now be achieved by, forexample, allowing the inner portion of the overall coating (e.g., thefirst thermoplastic polymer coating layer) to be responsible foradhering the overall coating to a particular substrate. In this way, thesecond thermoplastic polymer coating layer can then be prepared for thepurpose of providing other characteristics to the overall coating otherthan, for example, superior adhesion characteristics to a substrate,since the second thermoplastic polymer coating layer does not contactthe substrate, and only need adhere to the first thermoplastic polymercoating layer.

FIG. 16A is an illustration of an assembly comprising a first substrateand a second substrate, (equivalently referred to herein as first andsecond components or first and second parts) that are fastened togetherand, when sealed, a fillet seal is formed at the interface of the firstsubstrate and second substrate (interface referred to equivalentlyherein as “juncture”) of the assembly. Fillet seals are understood tooccur two interfacing substrates (e.g., at the interface at or betweento proximately located substrate surfaces, panels, etc.) The sealantapplied to the area of the fillet seal effectively seals any gap orspace at the interface.

Further, when the first and second substrates include exposed edges,edge seals may be required to ameliorate an undesirable phenomenon knownas “edge glow”. Edge glow can occur when substrate material at edges ofthe substrate are exposed. Fiber-based materials (e.g., composite basedmaterials that incorporate carbon fibers, boron fibers, aramid fibers,etc.), can be particularly susceptible to “edge glow”, as the exposedfiber ends at a component edge can behave as a cathode that emitselectrons to a degree that can approximate the electrical energy of aweak spark.

As shown in FIG. 16A and according to present aspects, the edges of suchmaterials are sealed by the presently disclosed two-layer sealants toform protective edge seals at the edges of the first and secondsubstrates. Additionally, filled seals are shown applied to theinterface of two substrates or components. As shown in FIG. 16A, anassembly 430 comprises a first substrate 432 and a second substrate 434that are joined (e.g., fastened together via fasteners 436). As shown inFIG. 16A, the first 432 and second 434 substrates are joined in anoverlapping orientation to form a lap joint. A two-layer thermoplasticpolymer sealant 437 that can also comprise, if desired, an amount ofconductive material (e.g., in either or both of the two layers presentin the two-layer thermoplastic sealant) for the purpose of delivering apredetermined resistivity to the thermoplastic polymer coating. Thetwo-layer thermoplastic sealant 437 is applied to the first 432 andsecond 434 substrates, such that a fillet seal 438 is formed at thefirst substrate 432 and second substrate 434 interface 439. As furthershown in FIG. 16A, first substrate edge 432 a, and a portion of secondsubstrate edge 434 a are also coated with the two-layer thermoplasticpolymer coating 437 (that can also comprise a predetermined amount ofconductive material for the purpose of delivering a predetermined andtailored resistivity value to the thermoplastic polymer coating) to forma first substrate edge seal 432 b and a second substrate edge seal 434b.

FIG. 16B is an enlarged cross-sectional view of the assembly 430 shownin FIG. 16A, and in particular taken across line 16B. As shown in FIG.16B, the two-layer thermoplastic sealant 437 comprises firstthermoplastic polymer coating layer 437 a applied to the first substrate432 and the second substrate 434, and a second thermoplastic polymercoating layer 437 b applied onto the first thermoplastic polymer coatinglayer 437 a. The cross-sectional view shown in FIG. 16B is forillustrative purposes only. According to present aspects, when thesecond thermoplastic polymer coating layer 437 b is applied to the firstthermoplastic polymer coating layer 437 b, depending on the temperatureat which the deposition occurs, a defined boundary between the first andsecond thermoplastic polymer coating layers may not be discernable asillustrated due to first and second thermoplastic polymers cominglingand bonding that can occur at the interface of the first and secondthermoplastic polymer layers.

FIGS. 17, 18, and 19 are illustrations of a portion of a fuel tankinterior 440, that can be an aircraft fuel tank interior, and showingrepresentative fuel tank components that can be, for example, a firstsubstrate 442 oriented proximate to a second substrate 444. As shown inFIGS. 17 and 18, the first substrate 442 is fastened to the secondsubstrate 444 via fasteners 446. A two-layer thermoplastic polymersealant 447 (that can also comprise a predetermined amount of conductivematerial for the purpose of delivering a predetermined and tailoredresistivity value to the thermoplastic polymer coating) is applied tothe first 442 and second 444 substrates, such that a fillet seal 448 isformed at the substrate interface 449 located at the juncture of thefirst substrate 442 and second substrate 444. Though not shown in FIGS.17 and 18, it is understood that, depending on the composition of thefirst and second substrates (442, 444), the two-layer thermoplasticpolymer sealant 447 could obtain an edge seal at the exposed edge of thefirst and/or second substrates 442, 444. That is, if either of the firstand/or second substrates 442, 444 comprise a fiber-based or othermaterial that could be susceptible to “edge glow” in the presence of acharge (e.g., an electrical charge caused by or resulting from an EME,etc.), the two-layer thermoplastic polymer sealant 447 can be applied toachieve the required edge seals at the edges of first and or secondsubstrates 442, 444.

FIG. 19 is an illustration of a fuel tank interior 450, that can be anaircraft fuel tank interior comprising fuel tank components and fueltank assemblies, showing a first substrate 452 oriented proximate to asecond substrate 454. As shown in FIG. 19, the first substrate 452 isfastened to the second substrate 454 via fasteners 456. A two-layerthermoplastic polymer sealant 457 (at least one layer of which can alsocomprise a predetermined amount of conductive material for the purposeof delivering a predetermined and tailored resistivity value to thethermoplastic polymer coating) is applied to the first 452 and second454 substrates, such that a fillet seal 458 is formed at the substrateinterface 459 located at the juncture of the first substrate 452 andsecond substrate 454. Though not specifically shown in FIG. 19, it isunderstood that, depending on the composition of the first and secondsubstrates (452, 454 respectively), the two-layer thermoplastic polymersealant 457 could obtain an edge seal at the exposed edge of the firstand/or second substrates 452, 454. That is, if either of the firstand/or second substrates 452, 454 comprise a fiber-based or othermaterial that could be susceptible to “edge glow” in the presence of acharge (e.g., an electrical charge caused by or resulting from an EME,etc.), the two-layer thermoplastic polymer sealant 457 can be applied toachieve the required edge seals at the edges of first and or secondsubstrates 452, 454.

According to aspects of the present disclosure, and as shown in FIGS.16A, 16B, 17, 18, and 19, when first substrate materials are made from amaterial having a resistivity value that differs from the resistivityvalue of the second substrate, and where the two substrates are joinedtogether, or are otherwise in close proximal contact, the variance inresistivities can result in damage at such junctures when EMEs occur(e.g., resulting from static discharge and/or lightning strikes), or atthe substrate edges. The conductive thermoplastic polymer sealantmaterials (e.g. equivalently referred to herein as the “sealants”) andseals placed as fillet seals between such first and second structuresand/or as end seals on such structures, as well as seals placed as edgeseals at first and/or second substrate edges ameliorate or eliminatedeleterious effects and damage otherwise caused by EMEs.

Further, the multi-layered thermoplastic seals and multi-layeredthermoplastic sealants disclosed herein afford many advantages overnon-thermoplastic sealants presently used in the manufacture ofsub-assemblies and assemblies that house, contain, store, or otherwisebecome exposed to harsh environmental factors and the presence ofchemicals, solvents, fuels, etc. (e.g., fuel tank, etc.). In otherwords, even when substrate materials have similar resistivities to oneanother and can allow static or other electrical charges to pass freelyand without incident from structure to structure, the multi-layeredthermoplastic seals and thermoplastic sealant materials disclosed hereinthat do not have a conductive component allow for improved sealingprocesses and improved seals and sealants as compared to known sealantsand sealant materials used, for example, in the manufacture of enclosedenvironments, including, without limitation, assemblies such as fueltanks, and aircraft fuel tanks, etc.

According to aspects of the present disclosure, when at least one of afirst and second substrate to be joined together (or that are orientedrelative to one another to form a seal requirement at the juncture ofthe substrates, or a seal requirement at the edges or one or moresubstrates) are made from materials having differing electricalresistivities (or electrical conductivities), a thermoplastic polymerfeedstock (that can be in a powdered form) is “doped” with apredetermined amount of conductive material to form a conductivethermoplastic polymer feedstock. As the conductive thermoplastic polymerfeedstock proceeds into and through the sprayer, the feedstockcomprising particles is subjected to heat and/or high velocity via gasjets to at least soften and deform the particles in the conductivethermoplastic polymer feedstock. The particles leave the sprayer as aparticulate spray at a predetermined velocity and impact a desiredtarget such as, for example, the areas where fillet seals and edge sealson a substrate or substrates are required. Upon impact on the selectedtarget(s) (e.g., substrate surfaces, etc.), the particulate spray formsa thermoplastic polymer coating, or thermoplastic polymer sealant, onthe substrates and forms a thermoplastic polymer seal.

The resistivity value of the thermoplastic polymer seals formed by thepresently disclosed multi-layered thermoplastic sealants formed can betailored or “tuned” to a desired resistivity value. In this way, if thecoated substrate materials are subjected to an electromagnetic effect(EME), such as, for example, from the electrical discharge of staticelectricity, or from a lightning strike, etc., the conductivity of thethermoplastic polymer sealant and seals will at least amelioratedeleterious effects from the EME that would otherwise be encountered ator near the fillet seals occurring at or near the substrate interfaces(e.g., adjoined structures), and at substrate material edge seals.

According to further present aspects, FIGS. 20A and 20B are flowchartsoutlining methods for forming a two-layer sealant material, with thesealant material comprising differing first and second thermoplasticpolymer layers, and with the first and second thermoplastic polymerlayers selected to have varying characteristics from one another. Morespecifically, FIG. 20A is a flowchart outlining a method for forming anddepositing a first thermoplastic polymer sealant layer onto a substratesurface, with the method 500 including, delivering 502 a at least onethermoplastic polymer feedstock to a high-velocity sprayer. The at leastone thermoplastic polymer feedstock can be in a powdered form. The firstthermoplastic polymer feedstock can include at least one of copolymersincluding Hytrel® TPC-ET (DuPont®), thermoplastic elastomers, andthermoplastic fluoroelastomers including DAI-EL® T-530 (Daikin®). Thedisclosed method as shown in FIG. 20A further includes forming 504 a afirst thermoplastic polymer sealant material and directing 506 a thefirst thermoplastic polymer sealant material from the high-velocitysprayer to a substrate surface, and depositing 508 a an amount of thefirst thermoplastic polymer sealant material onto the substrate to forma first thermoplastic polymer sealant layer. The high-velocity sprayerused to deposit the first thermoplastic polymer material onto thesubstrate can be controlled manually. In addition, according to furtheraspects, the high-velocity sprayer can be automatically controlled by arobot structure in communication with the high velocity sprayer.According to this optional aspect, shown as step 510 a in FIG. 20A,movement of the high-velocity sprayer can be directed by a robotstructure in communication with the high-velocity sprayer, with therobot structure further in communication with a controller. Thecontroller is understood to be in communication with required softwareand hardware typically used in the field of robotics.

FIG. 20B is a flowchart outlining a method according to aspects of thepresent disclosure, for forming and depositing a second thermoplasticpolymer sealant layer onto the first thermoplastic polymer sealantmaterial, with the method 600 including, delivering 502 b at least onethermoplastic polymer feedstock (that can be in a powdered form) for thesecond thermoplastic polymer sealant material layer to a high-velocitysprayer. The second thermoplastic polymer feedstock can include at leastone of polyetheretherketone, polyetherketoneketone, polyamide,polyphenylsulfide, polyphenylsulfone, polysulfone, and polyetheramide.The disclosed method as shown in FIG. 20BA further includes forming 504b a second thermoplastic polymer sealant material and directing 506 bthe second thermoplastic polymer sealant material from the high-velocitysprayer to the first thermoplastic polymer sealant material, anddepositing 508 b an amount of the second thermoplastic polymer sealantmaterial onto the first thermoplastic polymer sealant material to coatthe first thermoplastic polymer sealant material and form a two-layerthermoplastic polymer sealant material. Similar to the method describedand outlined in FIG. 20A, the high-velocity sprayer used to deposit thesecond thermoplastic polymer material onto the first thermoplasticpolymer layer can be controlled manually. In addition, according tofurther aspects, the high-velocity sprayer can be automaticallycontrolled by a robot structure in communication with the high velocitysprayer. According to this optional aspect, shown as step 510 b in FIG.20B, movement of the high-velocity sprayer can be directed by a robotstructure in communication with the high-velocity sprayer, with therobot structure further in communication with a controller. Thecontroller is understood to be in communication with required softwareand hardware typically used in the field of robotics. The methodoutlined in FIGS. 20A and 20B can be used to form the secondthermoplastic polymer material sealant and the resulting seals formedtherefrom as shown in any one or more of FIG. 1 through FIG. 19.

According to further present aspects, FIGS. 21A and 21B are flowchartsoutlining methods for forming a conductive two-layer thermoplasticpolymer seal made from a conductive two-layer thermoplastic polymersealant material, with the conductive two-layer thermoplastic polymerseal comprising differing first and second thermoplastic polymer layers,and with the first and second thermoplastic polymer layers of the sealselected to have varying characteristics from one another. Morespecifically, FIG. 21A is a flowchart outlining a method according toaspects of the present disclosure, with the method 760 including,delivering 602 a at least one thermoplastic polymer feedstock for afirst thermoplastic polymer sealant (that can be in a powdered form) toa high-velocity sprayer. The thermoplastic polymer feedstock can includeat least one of copolymers including Hytrel® TPC-ET (DuPont®),thermoplastic elastomers, and thermoplastic fluoroelastomers includingDAI-EL® T-530 (Daikin®). The disclosed method further includesdelivering 604 a a conductive feedstock material to the high-velocitysprayer, forming 606 a a conductive first thermoplastic polymer sealantmaterial and directing 608 a the conductive first thermoplastic polymersealant material from the high-velocity sprayer to a substrate surface,and depositing 610 a an amount of the conductive first thermoplasticpolymer sealant onto the substrate to form a first thermoplastic polymersealant layer. According to a further aspect shown as optional step 612a in FIG. 21A, movement of the high-velocity sprayer can be directed bya robot structure in communication with the high-velocity sprayer, withthe robot structure further in communication with a controller. Thecontroller is understood to be in communication with required softwareand hardware typically used in the field of robotics.

FIG. 21B is a flowchart outlining a method according to aspects of thepresent disclosure, with the method 770 including, delivering 602 b atleast one thermoplastic polymer feedstock for a first thermoplasticpolymer sealant (that can be in a powdered form) to a high-velocitysprayer. The second thermoplastic polymer feedstock includes at leastone of polyetheretherketone, polyetherketoneketone, polyamide,polyphenylsulfide, polyphenylsulfone, polysulfone, and polyetheramide.The disclosed method further includes delivering 604 b a conductivefeedstock material to the high-velocity sprayer, forming 606 b aconductive first thermoplastic polymer sealant material and directing608 b the conductive first thermoplastic polymer sealant material fromthe high-velocity sprayer to a substrate surface, and depositing 610 ban amount of the conductive first thermoplastic polymer sealant onto thesubstrate to form a first thermoplastic polymer sealant layer. Accordingto a further aspect shown as optional step 612 b in FIG. 21B, movementof the high-velocity sprayer can be directed by a robot structure incommunication with the high-velocity sprayer, with the robot structurefurther in communication with a controller. The controller is understoodto be in communication with required software and hardware typicallyused in the field of robotics. The methods outlined in FIGS. 21A and 21Bcan be used to form the thermoplastic polymer material and sealants andthe seals formed therefrom as shown in any one or more of FIG. 1 throughFIG. 20B.

Further present aspects contemplate using a single high-velocitysprayer, into which is first directed the first thermoplastic polymerfeedstock that will become the deposited first thermoplastic polymersealant layer that is deposited onto a substrate surface. According tothis aspect, the second thermoplastic polymer feedstock is directed tothe same high-velocity sprayer and the second thermoplastic polymermaterial exits the high velocity sprayer and is directed to coat thefirst thermoplastic polymer sealant layer and become the secondthermoplastic polymer sealant layer and complete the formation of thetwo-layer thermoplastic polymer sealant.

In addition, present aspects contemplate the use of more than onehigh-velocity sprayer, with a first high-velocity sprayer dedicated tothe deposition of the first thermoplastic polymer sealant material ontoa substrate surface; and a second high-velocity sprayer is thendedicated to the deposition of the second thermoplastic polymer sealantmaterial to form the second thermoplastic polymer sealant material layerthat is deposited onto the first thermoplastic polymer sealant layer.This aspect is illustrated in the method 800 outlined in FIG. 22comprising directing 802 the first thermoplastic polymer (feedstock) toa first high-velocity sprayer, depositing 804 the first thermoplasticpolymer to a substrate surface, and forming 806 a first thermoplasticpolymer coating layer on the substrate surface. This process is followedby directing 808 the second thermoplastic polymer (feedstock) to a firstor second high-velocity sprayer, depositing 810 the second thermoplasticpolymer onto the first thermoplastic polymer coating layer, forming 812a second thermoplastic polymer coating layer on the first thermoplasticpolymer coating layer, and forming 814 a two-layer sealant on thesubstrate surface, such sealant comprising first and secondthermoplastic coating layers.

Though not shown in FIG. 22, the movement of the first and secondhigh-velocity sprayers can be controlled and operated manually, or canbe automated, such as via robot arms or robotic structures incommunication with the high-velocity sprayers, as disclosed herein. Themethods outlined in FIG. 22 can be used to form the two-layerthermoplastic polymer material, coatings, sealants, and seals formedtherefrom as shown in any one or more of FIG. 1 through FIG. 21B.

According to another present aspect, the discrete layers of thepresently disclosed multi-layered coatings and sealants are depositedaccording to controlled regimens in view of the differingcharacteristics of the thermoplastic polymers that constitute each ofthe layers, and that are different from one another. For example, whenthe high-velocity sprayed used to deposit the thermoplastic layers arethermal sprayers, deposition temperatures imposed on the thermoplasticpolymers by the sprayer(s) are controlled and otherwise are operatedwithin a temperature range to preserve the desired characteristics ofthe resulting thermoplastic polymer layers in the resulting coatings andsealants.

In addition, present aspects contemplate methods for detecting andcontrolling substrate temperatures during the disclosed coatingprocesses. FIG. 23 outlines such aspects for the method 800 shown inFIG. 22, with additional steps for monitoring and maintaining asubstrate temperature in a temperature range to, for example, insurethat the deposited first and/or second thermoplastic polymer layers arenot exposed to a deleterious temperature that could otherwise adverselyimpact the performance of such deposited thermoplastic layers. Anillustrative method 800 is outlined in FIG. 23 comprising directing 802the first thermoplastic polymer (feedstock) to a first high-velocitysprayer, depositing 804 the first thermoplastic polymer to a substratesurface, and forming 806 a first thermoplastic polymer coating layer onthe substrate surface. The method 800 outlined in FIG. 23 furthercomprises monitoring 816 the temperature of the substrate surface andoptionally maintaining 818 the temperature of the substrate surface at atemperature ranging from about 120° F. to about 350° F., and morepreferably from about 120° F. to below about 250° F. The temperature ofthe substrate surface can continued to be monitored throughout theremainder of the outlined process that comprises directing 808 thesecond thermoplastic polymer (feedstock) to a first or secondhigh-velocity sprayer, depositing 810 the second thermoplastic polymeronto the first thermoplastic polymer coating layer, forming 812 a secondthermoplastic polymer coating layer on the first thermoplastic polymercoating layer, and forming 814 a two-layer sealant on the substratesurface, such sealant comprising first and second thermoplastic coatinglayers.

While present aspects describe and illustrate two-layer thermoplasticpolymer coating systems, resulting sealants, sealant materials, andseals, further aspects contemplate multi-layer thermoplastic polymercoating systems, resulting sealants, sealant materials, and seals havingtwo or more layers, with at least the first thermoplastic polymer layerthat contacts a substrate surface and the final thermoplastic polymerlayer that can be exposed to the environment comprising differentthermoplastic polymers, and with at least the first and finalthermoplastic polymer layers comprising differing predeterminedproperties and characteristics.

Further aspects of the present disclosure contemplate thermoplasticpolymer fastener coatings and conductive thermoplastic polymer fastenercoatings (and methods of their delivery to substrates and substratesurfaces comprising fasteners) and other components includingcomponents, assemblies, etc. for in structures and objects, including,for example, vehicles. Components for use in such assemblies andsub-assemblies comprising the presently disclosed coatings findparticular utility in the manufacture of vehicles, including aircraft,as well as structural components used in the manufacture of fuel tankson such vehicles.

Such contemplated components, assemblies etc. include, withoutlimitation, fasteners for installing, securing, etc. components,assemblies, etc. associated with aircraft (e.g. spars, ribs, stringers,etc.), with such components finding particular usefulness in connectionwith vehicle fuel tanks and fuel tank systems. Such vehicles include,without limitation, a manned aircraft, an unmanned aircraft, a mannedspacecraft, an unmanned spacecraft, a manned rotorcraft, an unmannedrotorcraft, a satellite, a rocket, a manned terrestrial vehicle, anunmanned terrestrial vehicle, a manned surface water borne vehicle, anunmanned surface water borne vehicle, a manned sub-surface water bornevehicle, an unmanned sub-surface water borne vehicle, and combinationsthereof.

Present aspects may, of course, be carried out in other ways than thosespecifically set forth herein without departing from essentialcharacteristics disclosed herein. The present aspects are to beconsidered in all respects as illustrative and not restrictive, and allchanges coming within the meaning and equivalency range of the appendedclaims are intended to be embraced therein.

What is claimed is:
 1. A seal for a substrate, said seal comprising: afirst thermoplastic polymer layer applied to a substrate, said firstthermoplastic polymer layer comprising a first thermoplastic polymer,said first thermoplastic polymer comprising at least one of: athermoplastic co-polyester, a co-polymer of vinylidene fluoride andhexafluoropropylene, a thermoplastic polyurethane, a thermoplasticvulcanizate, a thermoplastic polyolefin elastomer, a styrene blockco-polymer, a fluoroelastomer, and combinations thereof; a secondthermoplastic polymer layer deposited onto said first thermoplasticpolymer layer, said second thermoplastic polymer layer comprising asecond thermoplastic polymer, said second thermoplastic polymercomprising at least one of: a polyether ether ketone, a polyether ketoneketone, a polyamide, a polysulfone, a polyphenylsulphone, apolyetheramide, and combinations thereof; and wherein the firstthermoplastic polymer is different than the second thermoplasticpolymer.
 2. The seal of claim 1, wherein the first thermoplastic polymerlayer applied to the substrate comprises a modulus less than 1000 MPa,and wherein the second thermoplastic polymer layer deposited onto saidfirst thermoplastic polymer layer comprises a modulus of less than 4 MP.3. The seal of claim 1, wherein the first thermoplastic polymer layerapplied to the substrate comprises an adhesion value ranging from about10 lbs/in to about 30 lbs/in wide area in 90° peel test according toASTM D6862-11 (2016).
 4. The seal of claim 1, wherein the seal is atleast one of: a fillet seal and an edge seal.
 5. The seal of claim 1,wherein the second thermoplastic polymer layer comprises a resistivityranging from about 1×10e⁵ to about 1×10e⁸ ohm-m.
 6. The seal of claim 1,wherein the first thermoplastic polymer layer is configured to beapplied to the substrate via a high velocity sprayer.
 7. The seal ofclaim 1, wherein the second thermoplastic polymer layer is configured tobe deposited onto the first thermoplastic polymer layer via a highvelocity sprayer.
 8. An assembly comprising; a first substrate; a secondsubstrate joined to the first substrate; a multi-layer sealant locatedon at least one of the first substrate and the second substrate, saidmulti-layer sealant comprising: a first thermoplastic polymer layerapplied to a substrate, said first thermoplastic polymer layercomprising a first thermoplastic polymer, said first thermoplasticpolymer comprising at least one: of a thermoplastic co-polyester, aco-polymer of vinylidene fluoride and hexafluoropropylene, athermoplastic polyurethane, a thermoplastic vulcanizate, a thermoplasticpolyolefin elastomer, a styrene block co-polymer, a fluoroelastomer, andcombinations thereof; a second thermoplastic polymer layer depositedonto said first thermoplastic polymer layer, said second thermoplasticpolymer layer comprising at least one of: a polyether ether ketone, apolyether ketone ketone, a polyamide, a polysulfone, apolyphenylsulphone, a polyetheramide, and combinations thereof, andwherein the first thermoplastic polymer is different than the secondthermoplastic polymer.
 9. The assembly of claim 8, wherein at least oneof the first and second thermoplastic polymer layers comprises aresistivity ranging from about 1×10e⁵ to about 1×10e⁸ ohm-m.
 10. Theassembly of claim 8, wherein the first substrate and the secondsubstrate are configured to be joined together to form an interface,said interface located between the first substrate and the secondsubstrate.
 11. The assembly of claim 8, further comprising; a filletseal, said fillet seal comprising an amount of the multi-layer sealant.12. The assembly of claim 8, wherein at least one of the first substrateand second substrate comprises an edge seal, said edge seal, said edgeseal comprising an amount of the multi-layer sealant.
 13. The assemblyof claim 8, wherein at least one of the first substrate and the secondsubstrate comprises a fastener.
 14. The assembly of claim 8, wherein atleast one of the first substrate and the second substrate comprises atleast one of: aluminum; a fiber-reinforced composite material; andcombinations thereof.
 15. An object comprising the assembly of claim 8.16. The object of claim 15, wherein the object is a fuel tank component.17. A vehicle comprising the object of claim
 15. 18. The vehicle ofclaim 17, said vehicle comprising at least one of: a manned spacecraft;and unmanned spacecraft; a manned aircraft; an unmanned aircraft; amanned hovercraft; an unmanned hovercraft, a manned rotorcraft; anunmanned rotorcraft; a manned terrestrial vehicle; an unmannedterrestrial vehicle; a manned surface watercraft; an unmanned surfacewatercraft; a sub-surface watercraft; an unmanned sub-surfacewatercraft, a manned satellite; an unmanned satellite; and combinationsthereof.
 19. A method comprising: directing a first thermoplasticpolymer from a first thermoplastic polymer feedstock to a first highvelocity sprayer, said first thermoplastic polymer feedstock comprisingat least one of: thermoplastic co-polyester, a co-polymer of vinylidenefluoride and hexafluoropropylene, a thermoplastic polyurethane, athermoplastic vulcanizate, a thermoplastic polyolefin elastomer, astyrene block co-polymer, a fluoroelastomer, and combinations thereof;depositing the first thermoplastic polymer from the high velocitysprayer onto a substrate surface; forming a first thermoplastic polymerlayer on the substrate surface; directing a second thermoplastic polymerfrom a second thermoplastic polymer feedstock to the first high velocitysprayer or a second high velocity sprayer, said second thermoplasticpolymer feedstock comprising at least one of: a polyether ether ketone,a polyether ketone ketone, a polyamide, a polysulfone, apolyphenylsulphone, a polyetheramide, and combinations thereof;depositing the second thermoplastic polymer from the high velocitysprayer onto the first thermoplastic polymer layer; forming a secondthermoplastic polymer layer on the first thermoplastic polymer layer;forming a two-layer thermoplastic polymer seal on the substrate surface;and wherein the first thermoplastic polymer is different than the secondthermoplastic polymer.
 20. The method of claim 20, after the step offorming a first thermoplastic polymer layer on the substrate surface,further comprising; monitoring temperature of the substrate surface; andmaintaining the temperature of the substrate surface at a temperatureranging from about 120° F. to about 350° F.